Method of making a fuel cell device

ABSTRACT

The invention relates to a method of making fuel cell devices. Anode and cathode layers are applied on respective first and opposing second sides of a first portion of a first green ceramic layer, and a second green ceramic layer of thickness approximately equal to that of the anode and cathode layers is applied on a second portion of each of the first and second sides of the first green ceramic layer. A sacrificial layer is applied over each of the anode, cathode and second green ceramic layers, and a third green ceramic layer is applied over the sacrificial layers. The layered structure is heated to sinter all the layers and burn out the sacrificial layers. A pair of gas passages is thus formed with a thick sintered ceramic therebetween as a passive supporting portion and an anode, thin electrolyte and cathode therebetween as an active portion of the device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 12/117,622, filed May 8, 2008 and entitled FUEL CELL DEVICE ANDSYSTEM, the disclosure of which is incorporated herein by reference inits entirety as if completely set forth herein below. Pursuant to 37C.F.R. §1.78(a)(4), the present application also claims the benefit ofand priority to Provisional Application Ser. No. 60/917,262, filed onMay 10, 2007 and entitled SOLID OXIDE FUEL CELL DEVICE AND SYSTEM, whichis expressly incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to fuel cell devices and systems, and methods ofmanufacturing the devices, and more particularly, to a fuel cell devicein the form of a multi-layer monolithic Fuel Cell Stick™.

BACKGROUND OF INVENTION

Ceramic tubes have found a use in the manufacture of Solid Oxide FuelCells (SOFCs). There are several types of fuel cells, each offering adifferent mechanism of converting fuel and air to produce electricitywithout combustion. In SOFCs, the barrier layer (the “electrolyte”)between the fuel and the air is a ceramic layer, which allows oxygenatoms to migrate through the layer to complete a chemical reaction.Because ceramic is a poor conductor of oxygen atoms at room temperature,the fuel cell is operated at 700° C. to 1000° C., and the ceramic layeris made as thin as possible.

Early tubular SOFCs were produced by the Westinghouse Corporation usinglong, fairly large diameter, extruded tubes of zirconia ceramic. Typicaltube lengths were several feet long, with tube diameters ranging from ¼inch to ½ inch. A complete structure for a fuel cell typically containedroughly ten tubes. Over time, researchers and industry groups settled ona formula for the zirconia ceramic which contains 8 mol % Y₂O₃. Thismaterial is made by, among others, Tosoh of Japan as product TZ-8Y.

Another method of making SOFCs makes use of flat plates of zirconia,stacked together with other anodes and cathodes, to achieve the fuelcell structure. Compared to the tall, narrow devices envisioned byWestinghouse, these flat plate structures can be cube shaped, 6 to 8inches on an edge, with a clamping mechanism to hold the entire stacktogether.

A still newer method envisions using larger quantities of small diametertubes having very thin walls. The use of thin walled ceramic isimportant in SOFCs because the transfer rate of oxygen ions is limitedby distance and temperature. If a thinner layer of zirconia is used, thefinal device can be operated at a lower temperature while maintainingthe same efficiency. Literature describes the need to make ceramic tubesat 150 μm or less wall thickness.

There are several main technical problems that have stymied thesuccessful implementation of SOFCs. One problem is the need to preventcracking of the ceramic elements during heating. For this, the tubularSOFC approach is better than the competing “stack” type (made fromlarge, flat ceramic plates) because the tube is essentiallyone-dimensional. The tube can get hot in the middle, for example, andexpand but not crack. For example, a tube furnace can heat a 36″ longalumina tube, 4″ in diameter, and it will become red hot in the center,and cold enough to touch at the ends. Because the tube is heated evenlyin the center section, that center section expands, making the tubebecome longer, but it does not crack. A ceramic plate heated in thecenter only would quickly break into pieces because the center expandswhile the outside remains the same size. The key property of the tube isthat it is uniaxial, or one-dimensional.

A second key challenge is to make contact to the SOFC. The SOFC ideallyoperates at high temperature (typically 700-1000° C.), yet it also needsto be connected to the outside world for air and fuel, and also to makeelectrical connection. Ideally, one would like to connect at roomtemperature. Connecting at high temperature is problematic becauseorganic material cannot be used, so one must use glass seals ormechanical seals. These are unreliable, in part, because of expansionproblems. They can also be expensive.

Thus, previous SOFC systems have difficulty with at least the twoproblems cited above. The plate technology also has difficulty with theedges of the plates in terms of sealing the gas ports, and hasdifficulty with fast heating, as well as cracking. The tube approachresolves the cracking issue but still has other problems. An SOFC tubeis useful as a gas container only. To work it must be used inside alarger air container. This is bulky. A key challenge of using tubes isthat you must apply both heat and air to the outside of the tube; air toprovide the O₂ for the reaction, and heat to accelerate the reaction.Usually, the heat would be applied by burning fuel, so instead ofapplying air with 20% O₂ (typical), the air is actually partiallyreduced (partially burned to provide the heat) and this lowers thedriving potential of the cell.

An SOFC tube is also limited in its scalability. To achieve greater kVoutput, more tubes must be added. Each tube is a single electrolytelayer, such that increases are bulky. The solid electrolyte tubetechnology is further limited in terms of achievable electrolytethinness. A thinner electrolyte is more efficient. Electrolyte thicknessof 2 μm or even 1 μm would be optimal for high power, but is verydifficult to achieve in solid electrolyte tubes. It is noted that asingle fuel cell area produces about 0.5 to 1 volt (this is inherent dueto the driving force of the chemical reaction, in the same way that abattery gives off 1.2 volts), but the current, and therefore the power,depend on several factors. Higher current will result from factors thatmake more oxygen ions migrate across the electrolyte in a given time.These factors are higher temperature, thinner electrolyte, and largerarea.

SUMMARY OF THE INVENTION

The invention provides a method of making a fuel cell device comprisingproviding a first green ceramic layer having a first portion that willserve as an active electrolyte portion of the fuel cell device and asecond portion that will serve as a passive supporting portion of thefuel cell device. An anode layer is applied on a first side and acathode layer is applied on an opposing second side of the first portionof the first green ceramic layer, and a second green ceramic layer isapplied on the second portion of each of the first and second sides ofthe first green ceramic layer, wherein a thickness of the second greenceramic layers is approximately equal to a thickness of the anode layerand the cathode layer. A sacrificial layer is applied over each of theanode and the cathode layers and second green ceramic layers, and athird green ceramic layer is applied over each of the sacrificiallayers. The layered structure is heated to a temperature sufficient tosinter all the layers and burn out the sacrificial layers to form a pairof gas passages with a thick sintered ceramic therebetween in thepassive supporting portion and an anode, thin electrolyte and cathodetherebetween in the active electrolyte portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIGS. 1 and 1A depict, in side cross-sectional view and topcross-sectional view, respectively, one embodiment of a basic Fuel CellStick™ device of the invention, having a single anode layer, cathodelayer and electrolyte layer, and a hot zone between two end cold zones.

FIG. 2 depicts in perspective view a first end of one embodiment of aFuel Cell Stick™ device of the invention with a fuel supply tubeconnected thereto.

FIG. 3A depicts in perspective view a Fuel Cell Stick™ device accordingto one embodiment of the invention, but having modified ends.

FIG. 3B depicts in perspective view a fuel supply tube connected to onemodified end of the device of FIG. 3A.

FIG. 4A depicts in perspective view a metallurgical bonding attachmentmeans to a plurality of Fuel Cell Stick™ devices to make electricalconnection to positive and negative voltage nodes according to oneembodiment of the invention.

FIG. 4B depicts in schematic end view a connection between multiple FuelCell Stick™ devices according to one embodiment of the invention, whereeach Fuel Cell Stick™ device includes a plurality of anodes andcathodes.

FIG. 5 depicts in schematic end view a mechanical attachment means formaking the electrical connection to positive and negative voltage nodesaccording to one embodiment of the invention.

FIGS. 6A and 6B depict in perspective views an alternative embodimenthaving a single cold zone at one end of a Fuel Cell Stick™ device towhich fuel and air supply tubes are attached, with the other end beingin the hot zone.

FIGS. 7A and 7B are cross-sectional side and top views, respectively,illustrating a plurality of support pillars in the air and fuel passagesaccording to one embodiment of the invention.

FIGS. 7C and 7D are micrographs depicting the use of spherical balls inthe fuel and air passages as the support pillars according to anotherembodiment of the invention.

FIG. 8A depicts in cross-section one embodiment of the inventioncontaining two fuel cells connected externally in parallel.

FIG. 8B depicts in cross-sectional view another embodiment of theinvention similar to FIG. 8A, but having the two fuel cells connectedinternally in parallel through the use of vias.

FIGS. 9A and 9B depict in cross-sectional views a multi-fuel cell designaccording to an embodiment of the invention having shared anodes andcathodes, where FIG. 9A depicts three fuel cell layers connected inparallel and FIG. 9B depicts three fuel cells connected in series.

FIG. 10 depicts in schematic side view a Fuel Cell Stick™ deviceaccording to one embodiment of the invention having a fuel supply tubeconnected to a cold end of the device and a side of the device open inthe hot zone to an air passage for supply of heated air to the device inthe hot zone.

FIG. 10A depicts in schematic side view a variation of the embodiment ofFIG. 10, where the hot zone is positioned between opposing cold ends.

FIG. 10B depicts the Fuel Cell Stick™ device of FIG. 10A in topcross-sectional view taken along line 10B-10B.

FIGS. 11-24 schematically depict various embodiments of the invention,where FIG. 11 provides a key for the components depicted in FIGS. 12-24.

FIGS. 25A and 27A depict in schematic top plan view and FIG. 27B depictsin schematic side view a Fuel Cell Stick™ device according to oneembodiment of the invention having a panhandle design with an elongatesection at one cold end and a large surface area section at the opposinghot end.

FIGS. 25B and 26A depict in schematic top plan view and FIG. 26B depictsin schematic side view an alternative embodiment of the panhandle designhaving two elongate sections at opposing cold ends with a center largesurface area section in a central hot zone.

FIGS. 28A-28D depict a Fuel Cell Stick™ device according to oneembodiment of the invention, having a spiral or rolled, tubularconfiguration, where FIGS. 28A-28C depict the unrolled structure inschematic top view, end view and side view, respectively, and FIG. 28Ddepicts the spiral or rolled, tubular configuration in schematicperspective view.

FIGS. 29A-29G depict another alternative embodiment of the inventionwherein the Fuel Cell Stick™ device has a tubular concentric form, andwhere FIG. 29A depicts the device in schematic isometric view, FIGS.29B-29E depict cross-sectional views taken from FIG. 29A, FIG. 29Fdepicts an end view at the air input end, and FIG. 29G depicts an endview at the fuel input end.

FIG. 30A depicts in schematic cross-sectional side view an embodiment ofa Fuel Cell Stick™ device of the invention having an integrated pre-heatzone preceding an active zone in the hot zone, and FIGS. 30B and 30Cdepict the device of FIG. 30A in schematic cross-sectional view takenalong lines 30B-30B and 30C-30C, respectively.

FIGS. 31A-31C are similar to FIGS. 30A-30C, but depict two cold zoneswith a central hot zone.

FIGS. 32A-32B depict in schematic cross-sectional side view andschematic cross-sectional top view taken along line 32B-32B of FIG. 32A,respectively, an embodiment similar to that depicted in FIGS. 31A-31C,but further including pre-heat chambers extending between the fuel inletand the fuel passage and between the air inlet and the air passage, eachpre-heat chamber extending from the cold zone into the pre-heat zone ofthe hot zone.

FIGS. 33A-33C depict another embodiment of the invention for pre-heatingthe air and fuel, where FIG. 33A is a schematic cross-sectional sideview through the longitudinal center of the Fuel Cell Stick™ device,FIG. 33B is a schematic cross-sectional top view taken along line33B-33B of FIG. 33A, and FIG. 33C is a schematic cross-sectional bottomview taken along line 33C-33C of FIG. 33A.

FIGS. 34A and 34B depict in schematic oblique front view and schematicside view, respectively, an embodiment of the invention having multipleanodes and cathodes interconnected externally in series.

FIG. 35 depicts in schematic side view the structure of FIG. 34B doubledwith the two structures connected externally by metal stripes to providea series-parallel design.

FIGS. 36A and 36B depict in schematic side view and perspective viewanother embodiment of the invention including metal stripes to connectanodes and cathodes in series and/or parallel in the hot zone and longmetal stripes extending from the hot zone to the cold zone for makinglow temperature connection in the cold zones to the positive andnegative voltage nodes.

FIG. 37 depicts in schematic isometric view an embodiment similar tothat of FIG. 36B, but having a single cold zone for the air and fuelsupply connections and for the voltage node connection.

FIGS. 38A and 38B depict in schematic cross-sectional side view anembodiment of the invention having multiple exit gaps along the sides ofthe device for bake-out of organic material used to form passages withinthe structure.

FIG. 39 depicts in schematic cross-sectional end view another embodimentof the invention in which anode material is used as the supportingstructure, referred to as an anode-supported version of a Fuel CellStick™ device.

FIGS. 40A and 40B depict in schematic cross-sectional end view andschematic cross-sectional side view, respectively, an anode-supportedversion according to another embodiment of a Fuel Cell Stick™ device ofthe invention in which an open fuel passage is eliminated in favor of aporous anode that serves the function of conveying the fuel through thedevice.

FIGS. 41A and 41B depict in schematic cross-sectional end view andschematic cross-sectional top view, respectively, another embodiment ofan anode-supported version of a Fuel Cell Stick™ device of theinvention, in which multiple air passages are provided within theanode-supporting structure, and a single fuel passage is provided normalto the multiple air passages.

FIGS. 42A-42C depict in schematic cross-sectional view a method forforming an electrode layer in a passage of a Fuel Cell Stick™ device ofthe invention, according to one embodiment.

FIG. 43 depicts in schematic cross-sectional side view anotherembodiment of the invention in which the electrolyte layer is providedwith an uneven topography to increase the surface area available toreceive an electrode layer.

FIG. 44 depicts in schematic cross-sectional side view an alternativeembodiment of the invention for providing uneven topography on theelectrolyte layer.

FIG. 45A depicts in schematic top view and FIG. 45B depicts incross-sectional view through the hot zone an embodiment of a Fuel CellStick™ device of the invention having a plurality of fuel cells on eachof a left and right side of the device, with a bridging portiontherebetween.

FIGS. 46A and 46B depict in schematic perspective view and schematiccross-sectional view, respectively, another embodiment of a Fuel CellStick™ device of the invention having large exterior contact pads toprovide a large or wide path of low resistance for electrons to travelto the cold end of the device.

FIG. 47 depicts in schematic cross-sectional side view a Fuel CellStick™ device according to another embodiment of the invention having asingle exhaust passage for both spent fuel and air.

FIGS. 48A-48C depict an alternative embodiment referred to as an“end-rolled Fuel Cell Stick™ device” having a thick portion and a thinrolled portion, wherein FIG. 48A depicts the unrolled device inperspective view, FIG. 48B depicts the rolled device in cross-sectionalside view, and FIG. 48C depicts the rolled device in perspective view.

FIG. 49A depicts in schematic cross sectional side view an embodimentfor building a Fuel Cell Stick™ device using a wire between two ceramiclayers.

FIG. 49B depicts in schematic perspective view the device of FIG. 49Aafter lamination.

FIG. 49C depicts in schematic perspective view the device of FIG. 49Bafter the wire has been removed.

FIGS. 50A-50C depict in schematic cross sectional view anotherembodiment for building a Fuel Cell Stick™ device using a combination ofwire and gap-forming tape.

FIGS. 51 and 52A depict in schematic perspective view a Fuel Cell Stick™device passing through a furnace wall.

FIG. 52B depicts in schematic perspective view the portion of the FuelCell Stick™ device of 52B within the bounds of the furnace wall.

FIG. 52C depicts in schematic perspective view a portion of a tubularFuel Cell Stick™ device where it would pass through a furnace wall.

FIG. 53 depicts in schematic perspective view a Fuel Cell Stick™ devicepassing through a furnace wall made up of multiple layers.

FIG. 54 depicts in schematic perspective view a Fuel Cell Stick™ devicepassing through a furnace wall made up of multiple layers and an airgap.

FIGS. 55A-55E depict in schematic cross sectional view the assembly of aFuel Cell Stick™ device having a floating current collector.

FIGS. 56A and 56B are micrographs depicting zirconia balls supporting afloating current collector.

FIGS. 57A and 57B depict in schematic cross sectional view thebackfilling of the structure of FIG. 55D with anode or cathode particlessuspended in a viscous liquid to form an anode or cathode.

FIGS. 58A, 58B, and 58C are micrographs depicting a current collectornearly causing a blockage of a passage.

FIG. 59 depicts in schematic cross sectional view current collectors onthe surface of the anode and the cathode.

FIG. 60 depicts in schematic cross sectional view current collectorsburied in the surface of the anode and the cathode.

FIGS. 61A-61C depict a method of burying a current collector in an anodeor cathode.

FIG. 62 is schematic cross sectional view depicting a method ofachieving an individual layer of electrolyte having two thicknesses.

FIG. 62A is a detailed view of FIG. 62.

FIG. 63 is a micrograph depicting a top view of a current collector in ahatch pattern.

FIGS. 64 and 65 are micrographs depicting side and angledcross-sectional views of a current collector over a porous anode orcathode.

FIG. 66A is a schematic cross-sectional view of a tube slipped over theend of a Fuel Cell Stick™ device.

FIG. 66B is a schematic perspective view of the end of a Fuel CellStick™ device of FIG. 66A.

FIG. 67A is a schematic cross-sectional view of a connector, includingspring electrical contacts, positioned on the end of a Fuel Cell Stick™device.

FIG. 67B is a schematic perspective view of the connector of FIG. 67A.

FIGS. 68A and 68B are schematic perspective views depicting Fuel CellStick™ devices having four points of exit.

FIG. 69 is a micrograph depicting a current collector trace that hasbeen recessed into a porous anode or cathode.

FIG. 70 is micrograph image depicting a gap left after removing acarbon-wax sacrificial material.

DETAILED DESCRIPTION

In one embodiment, the invention provides a SOFC device and system inwhich the fuel port and the air port are made in one monolithicstructure. In one embodiment, the SOFC device is an elongate structure,essentially a relatively flat or rectangular stick (and thus, referredto as a Fuel Cell Stick™ device), in which the length is considerablygreater than the width or thickness. The Fuel Cell Stick™ devices arecapable of having cold ends while the center is hot (cold ends being<300° C.; hot center being >400° C., and most likely >700° C.). Slowheat conduction of ceramic can prevent the hot center from fully heatingthe colder ends. In addition, the ends are quickly radiating away anyheat that arrives there. The invention includes the realization that byhaving cold ends for connection, it is possible to make easierconnection to the anode, cathode, fuel inlet and H₂O CO₂ outlet, and airinlet and air outlet. While tubular fuel cell constructions are alsocapable of having cold ends with a hot center, the prior art does nottake advantage of this benefit of ceramic tubes, but instead, places theentire tube in the furnace, or the hot zone, such that high temperatureconnections have been required. The prior art recognizes the complexityand cost of making high temperature brazed connections for the fuelinput, but has not recognized the solution presented herein. The FuelCell Stick™ device of the invention is long and skinny so that it hasthe thermal property advantages discussed above that allow it to beheated in the center and still have cool ends. This makes itstructurally sound with temperature, and makes it relatively easy toconnect fuel, air and electrodes. The Fuel Cell Stick™ device isessentially a stand-alone system, needing only heat, fuel, and air to beadded in order to make electricity. The structure is designed so thatthese things can be readily attached.

The Fuel Cell Stick™ device of the invention is a multi-layer structureand may be made using a multi-layer co-fired approach, which offersseveral other advantages. First, the device is monolithic, which helpsto make it structurally sound. Second, the device lends itself totraditional high volume manufacturing techniques such as those used inMLCC (multi-layer co-fired ceramic) production of capacitor chips. (Itis believed that multi-layer capacitor production is the largest volumeuse of technical ceramics, and the technology is proven for high volumemanufacturing.) Third, thin electrolyte layers can be achieved withinthe structure at no additional cost or complexity. Electrolyte layers of2 μm thickness are possible using the MLCC approach, whereas it is hardto imagine a SOFC tube with less than a 60 μm electrolyte wallthickness. Hence, the Fuel Cell Stick™ device of the invention can beabout 30 times more efficient than a SOFC tube. Finally, the multi-layerFuel Cell Stick™ devices of the invention could each have many hundreds,or thousands, of layers, which would offer the largest area and greatestdensity.

Consider the surface area of a SOFC tube of the prior art versus a FuelCell Stick™ device of the invention. For example, consider a 0.25″diameter tube versus a 0.25″×0.25″ Fuel Cell Stick™ device. In the tube,the circumference is 3.14×D, or 0.785″. In the 0.25″ Fuel Cell Stick™device, the usable width of one layer is about 0.2 inches. Therefore, ittakes about 4 layers to give the same area as one tube. These figuresare dramatically different than those for capacitor technology. Thestate of the art for Japanese multi-layer capacitors is currently 600layers of 2 μm thicknesses. The Japanese will likely soon launch 1000layer parts in production, and they make them now in the laboratory.These chip capacitors with 600 layers are only 0.060″ (1500 μm).Applying this manufacturing technology to a Fuel Cell Stick™ device ofthe invention, in a 0.25″ device having a 2 μm electrolyte thickness andair/fuel passages with respective cathodes/anodes of 10 μm thickness, itwould be feasible to produce a single device with 529 layers. That wouldbe the equivalent of 132 tubes. Prior art strategies either add moretubes, increase diameter, and/or increase tube length to get more power,with result being very large structures for high power output. Theinvention, on the other hand, either adds more layers to a single FuelCell Stick™ device to get more power and/or uses thinner layers orpassages in the device, thereby enabling miniaturization for SOFCtechnology. Moreover, the benefit in the present invention is a squaredeffect, just like in capacitors. When the electrolyte layers are madehalf as thick, the power doubles, and then you can fit more layers inthe device so power doubles again.

Another key feature of the invention is that it would be easy to linklayers internally to increase the output voltage of the Fuel Cell Stick™device. Assuming 1 volt per layer, 12 volts output may be obtained bythe Fuel Cell Stick™ devices of the invention using via holes to linkgroups of 12 together. After that, further connections may link groupsof 12 in parallel to achieve higher current. This can be done withexisting methods used in capacitor chip technology. The criticaldifference is that the invention overcomes the brazing and complexwiring that other technologies must use.

The invention also provides a greater variety of electrode optionscompared to the prior art. Precious metals will work for both the anodesand cathodes. Silver is cheaper, but for higher temperature, a blendwith Pd, Pt, or Au would be needed, with Pd possibly being the lowestpriced of the three. Much research has focused on non-precious metalconductors. On the fuel side, attempts have been made to use nickel, butany exposure to oxygen will oxidize the metal at high temperature.Conductive ceramics are also known, and can be used in the invention. Inshort, the present invention may utilize any sort ofanode/cathode/electrolyte system that can be sintered.

In an embodiment of the invention, it is possible that when a large areaof 2 μm tape is unsupported, with air/gas on both sides, the layer mightbecome fragile. It is envisioned to leave pillars across the gap. Thesewould look something like pillars in caves where a stalactite andstalagmite meet. They could be spaced evenly and frequently, giving muchbetter strength to the structure.

For attachment of the gas and air supply, it is envisioned that the endtemperature is below 300° C., for example, below 150° C., such that hightemperature flexible silicone tubes or latex rubber tubes, for example,may be used to attach to the Fuel Cell Stick™ devices. These flexibletubes can simply stretch over the end of the device, and thereby form aseal. These materials are available in the standard McMaster catalog.Silicone is commonly used at 150° C. or above as an oven gasket, withoutlosing its properties. The many silicone or latex rubber tubes of amulti-stick Fuel Cell Stick™ system could be connected to a supply withbarb connections.

The anode material or the cathode material, or both electrode materials,may be a metal or alloy. Suitable metals and alloys for anodes andcathodes are known to those of ordinary skill in the art. Alternatively,one or both electrode materials may be an electronically conductivegreen ceramic, which are also known to those of ordinary skill in theart. For example, the anode material may be a partially sinteredmetallic nickel coated with yttria-stabilized zirconia, and the cathodematerial may be a modified lanthanum manganite, which has a perovskitestructure.

In another embodiment, one or both of the electrode materials may be acomposite of a green ceramic and a conductive metal present in an amountsufficient to render the composite conductive. In general, a ceramicmatrix becomes electronically conductive when the metal particles startto touch. The amount of metal sufficient to render the composite matrixconductive will vary depending mainly on the metal particle morphology.For example, the amount of metal will generally need to be higher forspherical powder metal than for metal flakes. In an exemplaryembodiment, the composite comprises a matrix of the green ceramic withabout 40-90% conductive metal particles dispersed therein. The greenceramic matrix may be the same or different than the green ceramicmaterial used for the electrolyte layer.

In the embodiments in which one or both electrode materials include aceramic, i.e., the electronically conductive green ceramic or thecomposite, the green ceramic in the electrode materials and the greenceramic material for the electrolyte may contain cross-linkable organicbinders, such that during lamination, the pressure is sufficient tocross-link the organic binder within the layers as well as to linkpolymer molecular chains between the layers.

Reference will now be made to the drawings in which like numerals areused throughout to refer to like components. Reference numbers used inthe Figures are as follows:

-   -   10 Full Cell Stick™ device    -   11 a First end    -   11 b Second end    -   12 Fuel inlet    -   13 Fuel pre-heat chamber    -   14 Fuel passage    -   16 Fuel outlet    -   18 Air inlet    -   19 Air pre-heat chamber    -   20 Air passage    -   21 Exhaust passage    -   22 Air outlet    -   24 Anode layer    -   25 Exposed anode portion    -   26 Cathode layer    -   27 Exposed cathode portion    -   28 Electrolyte layer    -   29 Ceramic    -   30 Cold zone (or second temperature)    -   31 Transition zone    -   32 Hot zone (or heated zone or first temperature zone)    -   33 a Pre-heat zone    -   33 b Active zone    -   34 Fuel supply    -   36 Air supply    -   38 Negative voltage node    -   40 Positive voltage node    -   42 Wire    -   44 Contact pad    -   46 Solder connection    -   48 Spring clip    -   50 Supply tube    -   52 Tie wrap    -   52 Support pillars    -   56 First via    -   58 Second via    -   60 Barrier coating    -   62 Surface particles    -   64 Textured surface layer    -   66 Anode suspension    -   70 Openings    -   72(a,b) Organic material/sacrificial layer    -   80 Left side    -   82 Right side    -   84 Bridging portion    -   90 Bridge    -   92 Wire (physical) Structure    -   94 Gap-forming tape    -   96 Furnace wall    -   96′ Multiple-layer furnace wall    -   96″ Multiple-layer furnace wall with air gap    -   98 a,b,c Insulation    -   100 Fuel Cell Stick™ device    -   102 Elongate section    -   104 Large surface area section    -   106 Elongate section    -   120 Air gap    -   122 Current collector    -   123 Gap    -   124 Electrode particles    -   126 Viscous fluid    -   128 Temporary substrate    -   130 Ceramic tape    -   132 Indentations    -   134 Connector    -   136 Electrical contacts    -   138 Gas flow pathway    -   140 O-ring    -   200 Spiral Tubular Fuel Cell Stick™ device    -   300 Concentric Tubular Fuel Cell Stick™ device    -   400 End-rolled Fuel Cell Stick™ device    -   402 Thick portion    -   404 Thin portion    -   500 Fuel Cell Stick™ device

The terms “zone,” “area,” and “region” may be used interchangeablythroughout, and are intended to have the same meaning. Similarly, theterms “passage,” “channel,” and “path” may be used interchangeablythroughout and the terms “outlet” and “exit” may be used interchangeablythroughout.

FIGS. 1 and 1A depict, in side cross-sectional view and topcross-sectional view, respectively, one embodiment of a basic Fuel CellStick™ device 10 of the invention, having a single anode layer 24,cathode layer 26 and electrolyte layer 28, wherein the device 10 ismonolithic. The Fuel Cell Stick™ device 10 includes a fuel inlet 12, afuel outlet 16 and a fuel passage 14 therebetween. Device 10 furtherincludes an air inlet 18, an air outlet 22 and an air passage 20therebetween. The fuel passage 14 and the air passage 20 are in anopposing and parallel relation, and the flow of fuel from fuel supply 34through the fuel passage 14 is in a direction opposite to the flow ofair from air supply 36 through air passage 20. The electrolyte layer 28is disposed between the fuel passage 14 and the air passage 20. Theanode layer 24 is disposed between the fuel passage 14 and theelectrolyte layer 28. Similarly, the cathode layer 26 is disposedbetween the air passage 20 and the electrolyte layer 28. The remainderof the Fuel Cell Stick™ device 10 comprises ceramic 29, which may be ofthe same material as the electrolyte layer 28 or may be a different butcompatible ceramic material. The electrolyte layer 28 is considered tobe that portion of the ceramic lying between opposing areas of the anode24 and cathode 26, as indicated by dashed lines. It is in theelectrolyte layer 28 that oxygen ions pass from the air passage 20 tothe fuel passage 14. As shown in FIG. 1, O₂ from the air supply 36travels through the air passage 20 and is ionized by the cathode layer26 to form 2O⁻, which travels through the electrolyte layer 28 andthrough the anode 24 into the fuel passage 14 where it reacts with fuel,for example, a hydrocarbon, from the fuel supply 34 to first form CO andH₂ and then to form H₂O and CO₂. While FIG. 1 depicts the reaction usinga hydrocarbon as the fuel, the invention is not so limited. Any type offuel commonly used in SOFCs may be used in the present invention. Fuelsupply 34 may be any hydrocarbon source or hydrogen source, for example.Methane (CH₄), propane (C₃H₈) and butane (C₄H₁₀) are examples ofhydrocarbon fuels.

For the reaction to occur, heat must be applied to the Fuel Cell Stick™device 10. In accordance with the invention, the length of the Fuel CellStick™ device 10 is long enough that the device can be divided into ahot zone 32 (or heated zone) in the center of the device 10 and coldzones 30 at each end 11 a and 11 b of the device 10. Between the hotzone 32 and the cold zones 30, a transition zone 31 exists. The hot zone32 will typically operate above 400° C. In exemplary embodiments, thehot zone 32 will operate at temperatures >600° C., for example >700° C.The cold zones 30 are not exposed to a heat source, and due to thelength of the Fuel Cell Stick™ device 10 and the thermal propertyadvantages of the ceramic materials, heat dissipates outside the hotzone 32, such that the cold zones 30 have a temperature <300° C. It isbelieved that heat transfer from the hot zone 32 down the length of theceramic to the end of the cold zone 30 is slow, whereas the heattransfer from the ceramic material outside the hot zone 32 into the airis relatively faster. Thus, most of the heat inputted in the hot zone 32is lost to the air (mainly in the transition zone 31) before it canreach the end of the cold zone 30. In exemplary embodiments of theinvention, the cold zones 30 have a temperature <150° C. In a furtherexemplary embodiment, the cold zones 30 are at room temperature. Thetransition zones 31 have temperatures between the operating temperatureof the hot zone 32 and the temperature of the cold zones 30, and it iswithin the transition zones 31 that the significant amount of heatdissipation occurs.

Because the dominant coefficient of thermal expansion (CTE) is along thelength of the Fuel Cell Stick™ device 10, and is therefore essentiallyone-dimensional, fast heating of the center is permitted withoutcracking. In exemplary embodiments, the length of the device 10 is atleast 5 times greater than the width and thickness of the device. Infurther exemplary embodiments, the length of the device 10 is at least10 times greater than the width and thickness of the device. In yetfurther exemplary embodiments, the length of the device 10 is at least15 times greater than the width and thickness of the device. Inaddition, in exemplary embodiments, the width is greater than thethickness, which provides for greater area. For example, the width maybe at least twice the thickness. By way of further example, a 0.2 inchthick Fuel Cell Stick™ device 10 may have a width of 0.5 inch. It may beappreciated that the drawings are not shown to scale, but merely give ageneral idea of the relative dimensions.

In accordance with the invention, electrical connections to the anode 24and cathode 26 are made in the cold zones 30 of the Fuel Cell Stick™device 10. In an exemplary embodiment, the anode 24 and the cathode 26will each be exposed to an outer surface of the Fuel Cell Stick™ device10 in a cold zone 30 to allow an electrical connection to be made. Anegative voltage node 38 is connected via a wire 42, for example, to theexposed anode portion 25 and a positive voltage node 40 is connected viaa wire 42, for example, to the exposed cathode portion 27. Because theFuel Cell Stick™ device 10 has cold zones 30 at each end 11 a, 11 b ofthe device, low temperature rigid electrical connections can be made,which is a significant advantage over the prior art, which generallyrequires high temperature brazing methods to make the electricalconnections.

FIG. 2 depicts in perspective view a first end 11 a of Fuel Cell Stick™device 10 with a supply tube 50 attached over the end 11 a and securedwith a tie wrap 52. Fuel from fuel supply 34 will then be fed throughthe supply tube 50 and into the fuel inlet 12. As a result of first end11 a being in the cold zone 30, flexible plastic tubing or other lowtemperature type connection material may be used to connect the fuelsupply 34 to the fuel inlet 12. The need for high temperature brazing tomake the fuel connection is eliminated by the invention.

FIG. 3A depicts in perspective view a Fuel Cell Stick™ device 10 similarto that depicted in FIG. 1, but having modified first and second ends 11a, 11 b. Ends 11 a, 11 b have been machined to form cylindrical endportions to facilitate connection of the fuel supply 34 and air supply36. FIG. 3B depicts in perspective view a supply tube 50 connected tothe first end 11 a for feeding fuel from fuel supply 34 to the fuelinlet 12. By way of example, supply tube 50 can be a silicone or latexrubber tube that forms a tight seal by virtue of its elasticity to thefirst end 11 a. It may be appreciated that the flexibility andelasticity of the supply tubes 50 can provide a shock-absorbing holderfor the Fuel Cell Stick™ devices 10 when the use is in a mobile devicesubject to vibrations. In the prior art, the tubes or plates wererigidly brazed, and thus subject to crack failure if used in a dynamicenvironment. Therefore, the additional function of the supply tubes 50as vibration dampers offers a unique advantage compared to the priorart.

Referring back to FIG. 3A, contact pads 44 are provided on the outersurface of the Fuel Cell Stick™ device 10 so as to make contact with theexposed anode portion 25 and the exposed cathode portion 27. Materialfor the contact pads 44 should be electrically conductive so as toelectrically connect the voltage nodes 38, 40 to their respective anode24 and cathode 26. It may be appreciated that any suitable method may beused for forming the contact pads 44. For example, metal pads may beprinted onto the outer surface of a sintered Fuel Cell Stick™ device 10.The wires 42 are secured to the contact pads 44 by a solder connection46, for example, to establish a reliable connection. Solders are a lowtemperature material, which can be used by virtue of being located inthe cold zones 30 of the Fuel Cell Stick™ device 10. For example, acommon 10Sn88Pb2Ag solder can be used. The present invention eliminatesthe need for high temperature voltage connections, thereby expanding thepossibilities to any low temperature connection material or means.

Also depicted in FIG. 3A, in perspective view, are the fuel outlet 16and the air outlet 22. The fuel enters through the fuel inlet 12 atfirst end 11 a, which is in one cold zone 30, and exits out the side ofFuel Cell Stick™ device 10 through outlet 16 adjacent the second end 11b. Air enters through air inlet 18 located in the second end 11 b, whichis in the cold zone 30, and exits from the air outlet 22 in the side ofthe Fuel Cell Stick™ device 10 adjacent the first end 11 a. While theoutlets 16 and 22 are depicted as being on the same side of the FuelCell Stick™ device 10, it may be appreciated that they may be positionedat opposing sides, for example, as depicted below in FIG. 4A.

By having air outlet 22 close to fuel inlet 12 (and similarly fueloutlet 16 close to air inlet 18), and through the close proximity of theoverlapping layers (anode, cathode, electrolyte), the air outlet 22functions as a heat exchanger, usefully pre-heating the fuel that entersthe device 10 through fuel inlet 12 (and similarly, fuel outlet 16pre-heats air entering through air inlet 18). Heat exchangers improvethe efficiency of the system. The transition zones 31 have overlappingareas of spent air and fresh fuel (and spent fuel and fresh air), suchthat heat is transferred before the fresh fuel (fresh air) reaches thehot zone 32. Thus, the Fuel Cell Stick™ device 10 of the invention is amonolithic structure that includes a built-in heat exchanger.

With respect to FIG. 4A, there is depicted in perspective view theconnection of a plurality of Fuel Cell Stick™ devices 10, in this casetwo Fuel Cell Stick™ devices 10, by aligning each contact pad 44connected to the exposed anode portions 25 and soldering (at 46) a wire42 connected to the negative voltage node 38 to each of the contact pads44. Similarly, the contact pads 44 that are connected to the exposedcathode portions 27 are aligned and a wire 42 connecting the positivevoltage node 40 is soldered (at 46) to each of those aligned contactpads 44, as shown partially in phantom. As may be appreciated, becausethe connection is in the cold zone 30, and is a relatively simpleconnection, if one Fuel Cell Stick™ device 10 in a multi-Fuel CellStick™ system or assembly needs replacing, it is only necessary to breakthe solder connections to that one device 10, replace the device with anew device 10, and re-solder the wires 42 to the contact pads 44 of thenew Fuel Cell Stick™ device 10.

FIG. 4B depicts in an end view the connection between multiple Fuel CellStick™ devices 10, where each Fuel Cell Stick™ device 10 includes aplurality of anodes 24 and cathodes 26. For example, the specificembodiment depicted in FIG. 4B includes three sets of opposing anodes 24and cathodes 26, with each anode 24 exposed at the right side of theFuel Cell Stick™ device 10 and each cathode 26 exposed at the left sideof the Fuel Cell Stick™ device 10. A contact pad 44 is then placed oneach side of the Fuel Cell Stick™ device 10 to contact the respectiveexposed anode portions 25 and exposed cathode portions 27. On the rightside, where the anodes 24 are exposed, the negative voltage node 38 isconnected to the exposed anode portions 25 by securing wire 42 to thecontact pad 44 via a solder connection 46. Similarly, positive voltagenode 40 is connected electrically to the exposed cathode portions 27 onthe left side of the Fuel Cell Stick™ device 10 by securing wire 42 tocontact pad 44 via the solder connection 46. Thus, while FIGS. 1-4Adepicted a single anode 24 opposing a single cathode 26, it may beappreciated, as shown in FIG. 4B, that each Fuel Cell Stick™ device 10may include multiple anodes 24 and cathodes 26, with each being exposedto an outer surface of the Fuel Cell Stick™ device 10 for electricalconnection by means of a contact pad 44 applied to the outer surface forconnection to the respective voltage node 38 or 40. The number ofopposing anodes 24 and cathodes 26 in the structure may be tens,hundreds and even thousands.

FIG. 5 depicts in an end view a mechanical attachment for making theelectrical connection between wire 42 and the contact pad 44. In thisembodiment, the Fuel Cell Stick™ devices 10 are oriented such that oneset of electrodes is exposed at the top surface of each Fuel Cell Stick™device 10. The contact pad 44 has been applied to each top surface atone end (e.g., 11 a or 11 b) in the cold zone 30. Spring clips 48 maythen be used to removably secure the wire 42 to the contact pads 44.Thus, metallurgical bonding may be used to make the electricalconnections, such as depicted in FIGS. 3A, 4A and 4B, or mechanicalconnection means may be used, as depicted in FIG. 5. The flexibility inselecting an appropriate attachment means is enabled by virtue of thecold zones 30 in the Fuel Cell Stick™ devices 10 of the invention. Useof spring clips 48 or other mechanical attachment means furthersimplifies the process of replacing a single Fuel Cell Stick™ device 10in a multi-stick assembly.

FIGS. 6A and 6B depict in perspective views an alternative embodimenthaving a single cold zone 30 at the first end 11 a of Fuel Cell Stick™device 10, with the second end 11 b being in the hot zone 32. In FIG.6A, the Fuel Cell Stick™ device 10 includes three fuel cells inparallel, whereas the Fuel Cell Stick™ device 10 of FIG. 6B includes asingle fuel cell. Thus, embodiments of the invention may include asingle cell design or a multi-cell design. To enable the single endinput of both the fuel and the air, the air inlet 18 is reoriented to beadjacent the first end 11 a at the side surface of the Fuel Cell Stick™device 10. The air passage 20 (not shown) again runs parallel to thefuel passage 14, but in this embodiment, the flow of air is in the samedirection as the flow of fuel through the length of the Fuel Cell Stick™device 10. At the second end 11 b of the device 10, the air outlet 22 ispositioned adjacent the fuel outlet 16. It may be appreciated thateither the fuel outlet 16 or the air outlet 22, or both, can exit from aside surface of the Fuel Cell Stick™ device 10, rather than both exitingat the end surface.

As depicted in FIG. 6B, the supply tube 50 for the air supply 36 isformed by making holes through the side of the supply tube 50 andsliding the device 10 through the side holes so that the supply tube 50for the air supply 36 is perpendicular to the supply tube 50 for thefuel supply 34. Again, a silicone rubber tube or the like may be used inthis embodiment. A bonding material may be applied around the jointbetween the supply tube 50 and the device 10 to form a seal. Theelectrical connections are also made adjacent the first end 11 a in thecold zone 30. FIGS. 6A and 6B each depict the positive voltageconnection being made on one side of the Fuel Cell Stick™ device 10 andthe negative voltage connection being made on the opposing side of theFuel Cell Stick™ device 10. However, it may be appreciated that theinvention is not so limited. An advantage of the single end input FuelCell Stick™ device 10 is that there is only one cold-to-hot transitioninstead of two transition zones 31, such that the Fuel Cell Stick™device 10 could be made shorter.

One benefit of the invention is the ability to make the active layersvery thin, thereby enabling a Fuel Cell Stick™ device 10 to incorporatemultiple fuel cells within a single device. The thinner the activelayers are, the greater the chance of an air passage 20 or fuel passage14 caving in during manufacture of the Fuel Cell Stick™ device 10,thereby obstructing flow through the passage 14 and/or 20. Therefore, inone embodiment of the invention, depicted in FIGS. 7A and 7B, aplurality of support pillars 54, for example ceramic support pillars,are provided in the passages 14 and 20 to prevent distortion of theelectrolyte layer 28 and obstruction of the passages 14, 20. FIG. 7A isa cross-sectional side view, whereas FIG. 7B is a cross-sectional topview through the air passage 20. According to one method of theinvention, using the tape casting method, a sacrificial tape layer maybe used, with a plurality of holes formed in the sacrificial layer, suchas by means of laser removal of the material. A ceramic material is thenused to fill the holes, such as by spreading a ceramic slurry over thesacrificial tape layer to penetrate the holes. After the various layersare assembled together, the sacrificial material of the sacrificiallayer is removed, such as by use of a solvent, leaving the supportpillars 54 remaining.

In another embodiment for forming the support pillars 54, largeparticles of a pre-sintered ceramic can be added to an organic vehicle,such as plastic dissolved in a solvent, and stirred to form a randommixture. By way of example and not limitation, the large particles maybe spheres, such as 0.002 in. diameter balls. The random mixture is thenapplied to the green structure, such as by printing in the areas wherethe fuel and air passages 14 and 20 are to be located. During thesintering (bake/fire) process, the organic vehicle leaves the structure(e.g. is burned out), thereby forming the passages 14, 20, and theceramic particles remain to form the support pillars 54 that physicallyhold open the passages 14, 20. The resultant structure is shown in themicrographs of FIGS. 7C and 7D. The support pillars 54 are randomlypositioned, with the average distance being a function of the loading ofthe ceramic particles in the organic vehicle.

FIG. 8A depicts in cross-section one embodiment of the inventioncontaining two fuel cells in parallel. Each active electrolyte layer 28has an air passage 20 and cathode layer 26 a or 26 b on one side and afuel passage 14 and anode layer 24 a or 24 b on the opposing side. Theair passage 20 of one fuel cell is separated from the fuel passage 14 ofthe second fuel cell by ceramic material 29. The exposed anode portions25 are each connected via wire 42 to the negative voltage node 38 andthe exposed cathode portions 27 are each connected via a wire 42 to thepositive voltage node 40. A single air supply 36 can then be used tosupply each of the multiple air passages 20 and a single fuel supply 34may be used to supply each of the multiple fuel passages 14. Theelectrical circuit established by this arrangement of the active layersis depicted at the right side of the figure.

In the cross-sectional view of FIG. 8B, the Fuel Cell Stick™ device 10is similar to that depicted in FIG. 8A, but instead of having multipleexposed anode portions 25 and multiple exposed cathode portions 27, onlyanode layer 24 a is exposed at 25 and only one cathode layer 26 a isexposed at 27. A first via 56 connects cathode layer 26 a to cathodelayer 26 b and a second via 58 connects anode layer 24 a to anode layer24 b. By way of example, laser methods may be used during formation ofthe green layers to create open vias, which are then subsequently filledwith electrically conductive material to form the via connections. Asshown by the circuit at the right of FIG. 8B, the same electrical pathis formed in the Fuel Cell Stick™ device 10 of FIG. 8B as in the FuelCell Stick™ device 10 of FIG. 8A.

FIGS. 9A and 9B also depict, in cross-sectional views, multi-fuel celldesigns, but with shared anodes and cathodes. In the embodiment of FIG.9A, the Fuel Cell Stick™ device 10 includes two fuel passages 14 and twoair passages 20, but rather than having two fuel cells, this structureincludes three fuel cells. The first fuel cell is formed between anodelayer 24 a and cathode layer 26 a with intermediate electrolyte layer28. Anode layer 24 a is on one side of a fuel passage 14, and on theopposing side of that fuel passage 14 is a second anode layer 24 b.Second anode layer 24 b opposes a second cathode layer 26 b with anotherelectrolyte layer 28 there between, thereby forming a second fuel cell.The second cathode layer 26 b is on one side of an air passage 20 and athird cathode layer 26 c is on the opposing side of that air passage 20.Third cathode layer 26 c opposes a third anode layer 24 c with anelectrolyte layer 28 therebetween, thus providing the third fuel cell.The portion of the device 10 from anode layer 24 a to cathode layer 26 ccould be repeated numerous times within the device 10 to provide theshared anodes and cathodes thereby multiplying the number of fuel cellswithin a single Fuel Cell Stick™ device 10. Each anode layer 24 a, 24 b,24 c includes an exposed anode portion 25 to which electricalconnections can be made at the outer surface of the Fuel Cell Stick™device 10 to connect to a negative voltage node 38 via a wire 42, forexample. Similarly, each cathode layer 26 a, 26 b, 26 c includes anexposed cathode portion 27 to the outside surface for connection to apositive voltage node 40 via a wire 42, for example. A single air supply36 may be provided at one cold end to supply each of the air passages 20and a single fuel supply 34 may be provided at the opposite cold end tosupply each of the fuel passages 14. The electrical circuit formed bythis structure is provided at the right side of FIG. 9A. This Fuel CellStick™ device 10 contains three fuel cell layers in parallel treblingthe available power. For example, if each layer produces 1 volt and 1amp, then each fuel cell layer produces 1 watt of power output(volt×amp=watt). Therefore, this three-layer layout would then produce 1volt and 3 amps for a total of 3 watts of power output.

In FIG. 9B, the structure of FIG. 9A is modified to provide a singleelectrical connection to each of the voltage nodes to create three fuelcells in series, as shown by the circuit at the right side of FIG. 9B.The positive voltage node 40 is connected to cathode layer 26 a atexposed cathode portion 27. Anode layer 24 a is connected to cathodelayer 26 b by via 58. Anode layer 24 b is connected to cathode layer 26c by via 56. Anode layer 24 c is then connected at exposed anode portion25 to the negative voltage node 38. Thus, using the same 1 amp/1 voltper layer assumption, this three cell structure would produce 3 voltsand 1 amp for a total of 3 watts of power output.

Another embodiment of the invention is depicted in side view in FIG. 10.In this embodiment, the Fuel Cell Stick™ device 10 has a single coldzone 30 at the first end 11 a with the second end 11 b being in the hotzone 32. As in other embodiments, the fuel inlets 12 are at the firstend 11 a and connected to a fuel supply 34 by a supply tube 50. In thisembodiment, the fuel passages 14 extend the length of the Fuel CellStick™ device 10 with the fuel outlet 16 being at second end 11 b. Thus,the fuel supply connection is made in the cold zone 30 and the outletfor the fuel reactants (e.g., CO₂ and H₂O) is in the hot zone 32.Similarly, the anodes have an exposed anode portion 25 in the cold zone30 for connecting to the negative voltage node 38 via a wire 42.

In the embodiment of FIG. 10, the Fuel Cell Stick™ device 10 is open atleast at one side, and potentially at both opposing sides, to provideboth air inlets 18 and air passages 20 in the hot zone 32. The use ofsupport pillars 54 may be particularly useful in this embodiment withinthe air passages 20. The air outlet can be at the second end 11 b, asdepicted. Alternatively, although not shown, the air outlet may be at anopposing side from the air inlet side if the passages 20 extend throughthe width and the air supply is directed only toward the input side, orif the passages 20 do not extend through the width. Instead of providingonly heat to the hot zone 32, in this embodiment, air is also provided.In other words, the sides of the device 10 in the hot zone 32 are opento heated air instead of supplying air through a forced air tube.

FIG. 10A shows in side view a variation of the embodiment depicted inFIG. 10. In FIG. 10A, the Fuel Cell Stick™ device 10 includes opposingcold zones 30 with a central heated zone 32 separated from the coldzones 30 by transition zones 31. The air inlet 18 is provided in thecentral heated zone 32, in at least a portion thereof, to receive theheated air. However, in this embodiment, the air passage 20 is notcompletely open to the side of the Fuel Cell Stick™ device 10 for anappreciable length as in FIG. 10. Rather, as shown more clearly in FIG.10B, air passage 20 is open in a portion of the hot zone 32 and then isclose to the sides for the remainder of the length and then exits at airoutlet 22 at second end 11 b of the Fuel Cell Stick™ device 10. Thisembodiment allows heated air to be supplied in the hot zone 32 ratherthan a forced air supply tube, but also allows for the fuel and air toexit at one end 11 b of the device 10 in a cold zone 30.

While specific embodiments have been depicted and described in detail,the scope of the invention should not be so limited. More generalembodiments of the invention are described below and may be understoodmore fully with reference to the schematic views depicted in FIGS.11-24. FIG. 11 provides a key for the components depicted schematicallyin FIGS. 12-24. Where fuel (F) or air (A) is shown by an arrow goinginto the Fuel Cell Stick™ device (e.g., SOFC Stick) that indicatesforced flow, such as through a tube connected to the input access point.Where air input is not depicted, that indicates that heated air issupplied in the hot zone by means other than a forced flow connectionand the Fuel Cell Stick™ device is open to the air passage at an accesspoint within the hot zone.

One embodiment of the invention is a Fuel Cell Stick™ device thatincludes at least one fuel passage and associated anode, at least oneoxidant pathway and associated cathode, and an electrolyte therebetween,where the cell is substantially longer than it is wide or thick so as tohave a CTE in one dominant axis and operating with a portion thereof ina heated zone having a temperature of greater than about 400° C. In thisembodiment, the Fuel Cell Stick™ device has integrated access points forboth air and fuel input at one end of the device according to thedominant CTE direction, or air input at one end and fuel input at theother end according to the dominant CTE direction, and air and fuelinputs being located outside the heated zone. For example, see FIGS. 20and 24.

In another embodiment of the invention, the fuel cell has a firsttemperature zone and a second temperature zone, wherein the firsttemperature zone is the hot zone, which operates at a temperaturesufficient to carry out the fuel cell reaction, and the secondtemperature zone is outside the heated zone and operates at a lowertemperature than the first temperature zone. The temperature of thesecond temperature zone is sufficiently low to allow low temperatureconnections to be made to the electrodes and a low temperatureconnection for at least the fuel supply. The fuel cell structure extendspartially into the first temperature zone and partially into the secondtemperature zone. For example, see FIGS. 12, 13 and 17.

In one embodiment of the invention, the fuel cell includes a firsttemperature zone that is the heated zone and a second temperature zoneoperating at a temperature below 300° C. The air and fuel connectionsare made in the second temperature zone using rubber tubing or the likeas a low temperature connection. Low temperature solder connections orspring clips are used to make the electrical connections to the anodeand cathode for connecting them to the respective negative and positivevoltage nodes. Further, the fuel outlet for carbon dioxide and water andthe air outlet for depleted oxygen are located in the first temperaturezone, i.e., the heated zone. For example, see FIG. 17.

In another embodiment, the fuel cell structure has a central firsttemperature zone that is the heated zone, and each end of the fuel cellis located outside the first temperature zone in a second temperaturezone operating below 300° C. Fuel and air inputs are located in thesecond temperature zone, as are solder connections or spring clips forelectrical connection to the anode and cathode. Finally, output for thecarbon dioxide, water and depleted oxygen are located in the secondtemperature zone. For example, see FIGS. 19, 20 and 24.

In another embodiment of the invention, fuel inputs may be provided ateach end according to the dominant CTE direction in a second temperaturezone operating below 300° C. with a first temperature zone being theheated zone provided in the center between the opposing secondtemperature zones. The output for the carbon dioxide, water, anddepleted oxygen may be located in the central heated zone. For example,see FIGS. 15 and 18. Alternatively, the output for the carbon dioxide,water and depleted oxygen may be located in the second temperature zone,i.e., outside of the heated zone. For example, see FIGS. 16 and 19.

In another embodiment, both the fuel and air input access points arelocated outside the first temperature zone, which is the heated zone, ina second temperature zone operating below 300° C. thereby allowing useof low temperature connections, such as rubber tubing for air and fuelsupply. In addition, solder connections or spring clips are used in thesecond temperature zone for connecting the voltage nodes to anodes andcathodes. In one embodiment, the fuel and air input are both at one endaccording to the dominate CTE direction, with the other end of the FuelCell Stick™ device being in the first heated temperature zone with theoutputs of carbon dioxide, water and depleted oxygen being in the heatedzone. For example, see FIG. 17. Thus, the Fuel Cell Stick™ device hasone heated end and one non-heated end.

In another embodiment, fuel and air are inputted into one end accordingto the dominant CTE direction outside the heated zone and exit at theopposite end also outside the heated zone, such that the heated zone isbetween two opposing second temperature zones. For example, see FIG. 20.In yet another alternative, fuel and air are inputted into both ofopposing ends located in second temperature zones with the fuel and airoutputs being in the central heated zone. For example, see FIG. 18.

In yet another alternative, fuel and air are inputted into both ofopposing ends located in second temperature zones with the respectiveoutputs being in the second temperature zone at the opposite end fromthe input. For example, see FIG. 19. Thus, the fuel cell has a centralheated zone and opposing ends outside the heated zone, with fuel and airboth inputted into the first end with the respective reaction outputsexiting adjacent the second end, and both fuel and air being inputtedinto the second end and the reaction outputs exiting adjacent the firstend.

In yet another embodiment, fuel input may be at one end outside theheated zone and air input may be at the opposite end outside the heatzone. For example, see FIGS. 21-24. In this embodiment, the reactionoutputs from both the air and fuel may be within the heated zone (seeFIG. 21), or they both may be outside the heated zone adjacent theopposite end from the respective input (see FIG. 24). Alternatively, thecarbon dioxide and water output may be in the hot zone while thedepleted oxygen output is outside the hot zone (see FIG. 22), orconversely, the depleted oxygen output may be in the heated zone and thecarbon dioxide and water output outside the heated zone (see FIG. 23).The variations with respect to fuel and air output depicted in FIGS. 22and 23 could also be applied in the embodiments depicted in FIGS. 18-20,for example.

In another embodiment of the invention, depicted in top plan view inFIGS. 25A and 27A and in side view in FIG. 27B, an Fuel Cell Stick™device 100 is provided having what may be referred to as a panhandledesign. The Fuel Cell Stick™ device 100 has an elongate section 102,which may be similar in dimension to the Fuel Cell Stick™ devices 10depicted in prior embodiments, that has a CTE in one dominant axis,i.e., it is substantially longer than it is wide or thick. The Fuel CellStick™ device 100 further has a large surface area section 104 having awidth that more closely matches the length. Section 104 may have asquare surface area or a rectangular surface area, but the width is notsubstantially less than the length, such that the CTE does not have asingle dominant axis in section 104, but rather has a CTE axis in thelength direction and the width direction. The large surface area section104 is located in the hot zone 32, whereas the elongate section 102 isat least partially located in the cold zone 30 and the transition zone31. In an exemplary embodiment, a portion of the elongate section 102extends into the hot zone 32, but this is not essential. By way ofexample, the fuel and air supplies 34,36 may be connected to theelongate section 102 in the manner depicted in FIG. 6B, as well as theelectrical connections.

In FIGS. 25B and 26A, a top plan view is provided and in FIG. 26B a sideview is provided of an alternative embodiment similar to that shown inFIGS. 25A, 27A and 27B but further having a second elongate section 106opposite the elongate section 102 so as to position the large surfacearea section 104 between the two elongate sections 102 and 106. Elongatesection 106 is also at least partially located in a cold zone 30 and atransition zone 31. In this embodiment, fuel may be inputted intoelongate section 102 and air inputted into elongate section 106. By wayof example, the air supply 36 and the fuel supply 34 could then beconnected to the elongate sections 106 and 102, respectively, in themanner depicted in FIG. 2 or FIG. 3B. As depicted in FIG. 25B, the airoutput may be located in the elongate section 102 adjacent the fuelinput, and the fuel output may be located in elongate section 106adjacent the air input. Alternatively, one or both of the air and fueloutputs may be located in the large surface area section 104 in the hotzone 32, as depicted in FIGS. 26A and 26B in top and side views,respectively. It may be appreciated that in the embodiments of FIGS. 25Aand 25B, the surface area of the opposing anode 24 and cathode 26 withintervening electrolyte 28 may be increased in the hot zone 32 toincrease the reaction area, thereby increasing the power generated bythe Fuel Cell Stick™ device 100.

Another benefit of the Fuel Cell Stick™ devices 10, 100 of the inventionis low weight. Typical combustion engines weigh on the order of 18-30lbs per kW of power. A Fuel Cell Stick™ device 10, 100 of the inventioncan be made with a weight on the order of 0.5 lbs per kW of power. FIGS.28A-28D depict an alternative embodiment of a Tubular Fuel Cell Stick™device 200 of the invention, having a spiral or rolled, tubularconfiguration. FIG. 28A is a schematic top view of device 200, in theunrolled position. The unrolled structure of device 200 has a first end202 and a second end 204 of equal length L that will correspond to thelength of the rolled or spiral Tubular Fuel Cell Stick™ device 200. Fuelinlet 12 and air inlet 18 are shown on opposing sides adjacent first end202. Fuel passage 14 and air passage 20 then extend along the width ofthe unrolled structure of device 200 to the second end 204 such that thefuel outlet 16 and air outlet 22 are at the second end 204, as furthershown in the schematic end view of the unrolled structure of device 200in FIG. 28B and the schematic side view of the unrolled structure ofdevice 200 in FIG. 28C. The fuel passage 14 and air passage 20 are shownas extending nearly the length L of the unrolled structure of device 200so as to maximize fuel and air flow, but the invention is not solimited. To form the spiral Tubular Fuel Cell Stick™ device 200, firstend 202 is then rolled toward second end 204 to form the spiral tubestructure of device 200 depicted in the schematic perspective view ofFIG. 28D. Air supply 36 may then be positioned at one end of the spiralTubular Fuel Cell Stick™ device 200 for input into air inlet 18, whilethe fuel supply 34 may be positioned at the opposite end of the spiralTubular Fuel Cell Stick™ device 200 to input fuel into the fuel inlet12. The air and the fuel will then exit the spiral Tubular Fuel CellStick™ device 200 along the length L of the device 200 through fueloutlet 16 and air outlet 22. The voltage nodes 38, 40 can be soldered tocontact pads 44 formed on or adjacent to opposing ends of the spiralTubular Fuel Cell Stick™ device 200.

FIGS. 29A-29G depict an alternative embodiment of the invention whereinthe Fuel Cell Stick™ device is in a tubular concentric form. FIG. 29Adepicts in schematic isometric view a concentric Tubular Fuel CellStick™ device 300. FIGS. 29B-29E depict cross-sectional views of theconcentric device 300 of FIG. 29A. FIG. 29F depicts an end view at theair input end of the device 300, and FIG. 29G depicts an end view at thefuel input end of device 300. The particular embodiment shown includesthree air passages 20, one being in the center of the tubular structureand the other two being spaced from and concentric therewith. Theconcentric Tubular Fuel Cell Stick™ device 300 also has two fuelpassages 14 between and concentric with the air passages 20. As shown inFIGS. 29A-29D, the concentric Tubular Fuel Cell Stick™ device 300includes a fuel outlet 16 connecting the fuel passages 14 at one end andan air outlet 22 connecting the air passages 20 at the other endopposite their respective inlets 12, 18. Each air passage 20 is linedwith cathodes 26 and each fuel passage 14 is lined with anodes 24, withelectrolyte 28 separating opposing anodes and cathodes. As shown inFIGS. 29A-29B and 29F-29G, electrical connection may be made to theexposed anodes 25 and exposed cathodes 27 at opposing ends of theconcentric Tubular Fuel Cell Stick™ device 300. Contact pads 44 may beapplied to the ends to connect the exposed anodes 25 and exposedcathodes 27, and although not shown, the contact pads 44 can be runalong the outside of the device 300 to permit the electrical connectionto be made at a point along the length of the device 300 rather than atthe ends. Concentric Tubular Fuel Cell Stick™ device 300 may includesupport pillars 54 positioned within the air and fuel passages 14, 20for structural support.

In the embodiments of the invention having two cold zones 30 at opposingends 11 a, 11 b, with air input and fuel output at one end and fuelinput and air output at the opposing end, the spent fuel or air is in aheated state as it exits the central hot zone 32. The heated air andfuel cool as they travel through the transition zones 31 to the coldzones 30. Thin layers of electrodes and/or ceramic/electrolyte separatean air passage 20 from a parallel fuel passage 14, and vice-versa. Inone passage, heated air is exiting the hot zone 32, and in an adjacentparallel passage, fuel is entering the hot zone 32, and vice-versa. Theheated air, through heat exchange principles, will heat up the incomingfuel in the adjacent parallel passage, and vice-versa. Thus, there issome pre-heating of the air and fuel through heat exchange. However, dueto the rapid loss of heat outside the hot zone 32, as discussed above,heat exchange may not be sufficient to pre-heat the air and fuel to theoptimal reaction temperature before it enters the active region in thehot zone 32. In addition, in embodiments where the Fuel Cell Stick™device 10 includes one cold end (cold zone 30) and one hot end (hot zone32), fuel and air are inputted into the same cold end 30 and exitthrough the same opposing hot end 32, such that there is no cross-flowof fuel and air for heat-exchange to occur. Only limited heat exchangeto the incoming fuel and air is available from the electrode and ceramicmaterials of the Fuel Cell Stick™ device 10.

FIGS. 30A-33C depict various embodiments of an Fuel Cell Stick™ device10 having integrated pre-heat zones 33 a for heating the fuel and airbefore it enters an active zone 33 b in which the anodes 24 and cathodes26 are in opposing relation. These embodiments include Fuel Cell Stick™devices 10 in which there are two cold ends 30 with an intermediate hotzone 32 and fuel and air input at opposing cold ends 30, and Fuel CellStick™ devices 10 in which there is one hot end 32 and one cold end 30with fuel and air input both at the single cold end 30. In theseembodiments, the amount of electrode material used can be limited to theactive zone 33 b with only a small amount leading to the cold zone 30for the external connection to the voltage nodes 38, 40. Another benefitin these embodiments, which will be described in more detail later, isthat the electrons have the shortest possible path to travel to theexternal voltage connection, which provides a low resistance.

FIG. 30A depicts a schematic cross-sectional side view of a firstembodiment of a Fuel Cell Stick™ device 10 having one cold zone 30 andone opposing hot zone 32 with an integrated pre-heat zone 33 a. FIG. 30Bdepicts in cross-section a view through the anode 24 looking up towardthe fuel passage 14, and FIG. 30C depicts in cross-section a viewthrough the cathode 26 looking down toward the air passage 20. As shownin FIGS. 30A and 30B, the fuel from fuel supply 34 enters through fuelinlet 12 and extends along the length of the device 10 through fuelpassage 14 and exits from the opposite end of the device 10 through fueloutlet 16. The cold zone 30 is at the first end 11 a of Fuel Cell Stick™device 10 and the hot zone 32 is at the opposing second end 11 b.Between the hot and cold zones is the transition zone 31. The hot zone32 includes an initial pre-heat zone 33 a through which the fuel firsttravels, and an active zone 33 b that includes the anode 24 adjacent thefuel passage 14. As shown in FIG. 30B, the cross-sectional area of theanode 24 is large in the active zone 33 b. The anode 24 extends to oneedge of the Fuel Cell Stick™ device 10 and an external contact pad 44extends along the outside of the device 10 to the cold zone 30 forconnection to the negative voltage node 38.

Similarly, as shown in FIGS. 30A and 30C, the air from air supply 36enters through the air inlet 18 positioned in the cold zone 30 and theair extends along the length of the Fuel Cell Stick™ device 10 throughair passage 20 and exits from the hot zone 32 through the air outlet 22.Because the air and fuel are entering at the same end and travelingalong the length of the Fuel Cell Stick™ device 10 in the samedirection, there is limited pre-heating of the air and fuel by heatexchange prior to the hot zone 32. The cathode 26 is positioned in theactive zone 33 b in opposing relation to the anode 24 and extends to theopposite side of the Fuel Cell Stick™ device 10 where it is exposed andconnected to an external contact pad 44 that extends from the active hotzone 33 b to the cold zone 30 for connection to the positive voltagenode 40. It is not necessary, however, that the exposed cathode 27 be onan opposite side of the device 10 as the exposed anode 25. The exposedanode 25 and exposed cathode 27 could be on the same side of the device10 and the contact pads 44 could be formed as stripes down the side ofthe Fuel Cell Stick™ device 10. By this structure, the air and fuel arefirst heated in the pre-heat zone 33 a, where no reaction is takingplace, and the majority of the anode and cathode material is limited tothe active zone 33 b where the heated air and fuel enters and react byvirtue of the opposed anode and cathode layers 24, 26.

The embodiment depicted in FIGS. 31A-31C is similar to that depicted inFIGS. 30A-30C, but rather than having one hot end 32 and one cold end30, the embodiment of FIGS. 31A-C includes opposing cold zones 30 with acentral hot zone 32. Fuel from fuel supply 34 enters through the firstend 11 a of device 10 through fuel inlet 12 in the cold zone 30 andexits from the opposite second end 11 b through fuel outlet 16positioned in the opposing cold zone 30. Similarly, air from air supply36 enters through the opposite cold zone 30 through air inlet 18 andexits at the first cold zone 30 through air outlet 22. The fuel entersthe hot zone 32 and is pre-heated in pre-heat zone 33 a, while the airenters at the opposite side of the hot zone 32 and is pre-heated inanother pre-heat zone 33 a. There is thus a cross-flow of fuel and air.The anode 24 opposes the cathode 26 in an active zone 33 b of hot zone32 and the reaction occurs in the active zone 33 b involving thepre-heated fuel and air. Again, the majority of electrode material islimited to the active zone 33 b. The anode 24 is exposed at one edge ofthe Fuel Cell Stick™ device 10, and the cathode 26 is exposed at theother side of device 10. An external contact pad 44 contacts the exposedanode 25 in the hot zone 32 and extends toward the first cold end 11 afor connection to negative voltage node 38. Similarly, an externalcontact pad 44 contacts the exposed cathode 27 in hot zone 32 andextends toward the second cold end 11 b for connection to positivevoltage node 40.

The pre-heat zones 33 a provide the advantage of fully heating the gasto the optimal reaction temperature before it reaches the active region.If the fuel is colder than the optimum temperature, the efficiency ofthe SOFC system will be lower. As the air and fuel continue on theirpaths, they warm up. As they warm up, the efficiency of the electrolyte28 increases in that region. When the fuel, air and electrolyte 28 reachthe full temperature of the furnace, then the electrolyte 28 is workingunder its optimal efficiency. To save money on the anode 24 and cathode26, which may be made out of precious metal, the metal can be eliminatedin those areas that are still below the optimal temperature. The amountof the pre-heat zone 33 a, in terms of length or other dimensions,depends on the amount of heat transfer from the furnace to the Fuel CellStick™ device 10, and from the Fuel Cell Stick™ device 10 to the fueland air, as well as whether any heat exchange is occurring due tocross-flow of the fuel and air. The dimensions further depend on therate of flow of fuel and air; if the fuel or air is moving quickly downthe length of the Fuel Cell Stick™ device 10, a longer pre-heat zone 33a will be advantageous, whereas if the flow rate is slow, the pre-heatzone 33 a may be shorter.

FIGS. 32A and 32B depict an embodiment similar to that shown in FIGS.31A-31C, but the Fuel Cell Stick™ device 10 includes a pre-heat chamber13 between the fuel inlet 12 and fuel passage 14 that extends into thehot zone 32 for pre-heating in the pre-heat zone 33 a a large volume offuel before it passes through the more narrow fuel passage 14 into theactive zone 33 b. The Fuel Cell Stick™ device 10 similarly includes apre-heat chamber 19 between the air inlet 18 and the air passage 20 thatextends into the hot zone 32 for pre-heating a large volume of air inthe pre-heat zone 33 a before it passes through the more narrow airpassage 20 to the active zone 33 b. As disclosed in embodiments above,the Fuel Cell Stick™ device 10 may include multiple fuel passages 14 andair passages 20, each of which would receive flow from a respectivepre-heat chamber 13, 19.

With respect to a high-volume pre-heat chamber 13, 19 instead of apre-heat channel, it may be imagined, by way of example only, that if ittakes 5 seconds for a molecule of air to heat up to the optimaltemperature, then if the molecules of air are traveling down the FuelCell Stick™ device 10 at 1 inch per second, the Fuel Cell Stick™ device10 would need a pre-heat channel that is 5 inches in length before theair enters the active zone 33 b. If, however, a large volume chamber isprovided instead of a channel, the volume permits the molecules to spendadditional time in the cavity before entering the more narrow channel tothe active zone 33 b, such that the air molecules are heated in thechamber and then a short length of channel may be used for feeding theheated air molecules to the active zone 33 b. Such a cavity or pre-heatchamber 13, 19 could be prepared in a number of different ways,including taking a green (i.e., before sintering) assembly and drillinginto the end of the assembly to form the chamber, or by incorporating alarge mass of organic material within the green stack as it is formed,whereby the organic material is baked out of the Fuel Cell Stick™ deviceduring sintering.

FIGS. 33A-33C depict yet another embodiment for pre-heating the air andfuel prior to the air and fuel reaching the active zone 33 b. FIG. 33Ais a schematic cross-sectional side view, essentially through thelongitudinal center of the Fuel Cell Stick™ device 10. FIG. 33B is across-sectional top view taken along the line 33B-33B where the fuelpassage 14 and anode 24 intersect, while FIG. 33C is a cross-sectionalbottom view taken along the line 33C-33C where the air passage 20intersects the cathode 26. The Fuel Cell Stick™ device 10 has twoopposing cold zones 30 and a central hot zone 32, with a transition zone31 between each cold zone 30 and the hot zone 32. Fuel from fuel supply34 enters the first end 11 a of Fuel Cell Stick™ device 10 through fuelinlet 12 and travels through the fuel passage 14, which extends towardthe opposite end of the hot zone 32, where it makes a U-turn and travelsback to the cold zone 30 of first end 11 a, where the spent fuel exitsthrough fuel outlet 16. Similarly, air from air supply 36 enters thesecond end 11 b of Fuel Cell Stick™ device 10 through the air inlet 18and travels through the air passage 20, which extends toward theopposing end of the hot zone 32, where it makes a U-turn and travelsback to the second end 11 b, where the air exits from the cold zone 30through air outlet 22. By means of these U-turned passages, the portionof the fuel passage 14 and air passage 20 from the initial entry intothe hot zone 32 through the bend (U-turn) constitute a pre-heat zone forheating the fuel and air. After the bends, or U-turns, in the passages14, 20, the passages are lined with a respective anode 24 or cathode 26,which are in opposing relation with an electrolyte 28 therebetween,which region constitutes the active zone 33 b in hot zone 32. Thus, thefuel and air is heated in the pre-heat zone 33 a prior to entry into theactive zone 33 b to increase the efficiency of the Fuel Cell Stick™device 10, and to minimize the usage of electrode material. The anode 24is extended to the exterior of the device 10 in the cold zone 30 forconnection to negative voltage node 38. Similarly, cathode 26 isextended to the exterior of the device 10 for electrical connection topositive voltage node 40. The fuel and air outlets 16 and 22 also mayexit from the cold zones 30.

In many of the embodiments shown and described above, the anodes 24 andcathodes 26 travel within the layers of the Fuel Cell Stick™ device 10,essentially in the center area of each layer, i.e., internal to thedevice, until they reach the end of the device. At that point, theanodes 24 and cathodes 26 are tabbed to the outside of the Fuel CellStick™ device 10 where the exposed anode 25 and exposed cathode 27 aremetallized with a contact pad 44, such as by applying a silver paste,and then a wire is soldered to the contact pad 44. For example, seeFIGS. 4A-4B. It may be desirable, however, to build up the layers in theFuel Cell Stick™ device 10 into higher voltage combinations, for exampleas shown in FIGS. 8A-9B. If it is desired to make a Fuel Cell Stick™device 10 that produces 1 KW of power, the power is divided between thevoltage and the current. One standard is to use 12 volts, such that 83amps would be needed to create the total 1 KW of power. In FIGS. 8B and9B, vias were used to interconnect the electrode layers to form parallelor series combinations.

Alternative embodiments for interconnecting the electrode layers aredepicted in FIGS. 34A to 37. Rather than interconnecting the electrodelayers in the interior of the Fuel Cell Stick™ device 10, thesealternative embodiments use exterior stripes (narrow contact pads), forexample of silver paste, along the sides of the Fuel Cell Stick™ device10, in particular, multiple small stripes. Using the striping technique,a simple structure is formed that can provide series and/or parallelcombinations to achieve any current/voltage ratios needed. Moreover, theexternal stripes will have loose mechanical tolerances compared to theinternal vias, thereby simplifying manufacturing. Also, the externalstripes will likely have a lower resistance (or equivalent seriesresistance) than the vias. Lower resistance in a conductor path willresult in lower power loss along that path, such that the externalstripes provide the ability to remove the power from the Fuel CellStick™ device 10 with a lower loss of power.

Referring now specifically to FIGS. 34A and 34B, an externalanode/cathode interconnect in series is depicted. FIG. 34A provides aschematic oblique front view of the alternating anodes 24 a, 24 b, 24 cand cathodes 26 a, 26 b, 26 c. Along the length of the Fuel Cell Stick™device 10, the anodes 24 a, 24 b, 24 c and cathodes 26 a, 26 b, 26 cinclude a tab out to the edge of the device 10 to provide the exposedanodes 25 and exposed cathodes 27. An external contact pad 44 (orstripe) is then provided on the outside of the Fuel Cell Stick™ device10 over the exposed anodes 25 and cathodes 27, as best shown in theschematic side view of FIG. 34B. By connecting the three pairs ofopposed anodes 24 a, 24 b, 24 c and cathodes 26 a, 26 b, 26 c in series,the Fuel Cell Stick™ device 10 provides 3 volts and 1 amp. In FIG. 35,the structure is doubled and the two structures are connected by longstripes down the sides of the device 10, thereby providing an externalanode/cathode interconnect in a series parallel design that provides 3volts and 2 amps.

FIGS. 36A and 36B provide an embodiment for a low equivalent seriesresistance path for providing low power loss. In this embodiment, thehot zone 32 is in the center of the Fuel Cell Stick™ device 10 with thefirst end 11 a and second end 11 b being in cold zones 30. Fuel isinputted through fuel inlets 12 in first end 11 a and air is inputtedthrough air inlets 18 in second end 11 b. Within the hot zone 32, whichis the active area of the Fuel Cell Stick™ device 10, the anodes 24 andcathodes 26 are exposed to the sides of the device 10, with the anodes24 exposed to one side, and the cathodes 26 exposed to the oppositeside. Contact pads 44 (or stripes) are applied over the exposed anodes25 and cathodes 27. Then, the edges of the Fuel Cell Stick™ device 10are metallized along the length of the sides of the device 10 until themetallization reaches the cold zones 30, where the low temperaturesolder connection 46 is made to the negative voltage node 38 and thepositive voltage node 40. The anodes 24 and cathodes 26 cannot beoptimized only for low resistance because they have other functions. Forexample, the electrodes must be porous to allow the air or fuel to passthrough to the electrolyte 28, and porosity increases resistance.Further, the electrodes must be thin to allow for good layer density ina multi-layer Fuel Cell Stick™ device 10, and the thinner the electrode,the higher the resistance. By adding thicker contact pads 44 to theedges (sides) of the Fuel Cell Stick™ device 10, it is possible toprovide a low resistance path toward the solder connection 46. Thethicker the contact pad 44, the lower the resistance. If an electronmust travel 10 inches, for example, down the electrode within the FuelCell Stick™ device 10, past all the voids in the electrode layer, thepath of least resistance would be to travel 0.5 inch, for example, tothe side edge of the device 10, and then travel the 10 inches down theexternal non-porous contact pad 44. Thus, the long contact pads 44 alongthe exterior of the Fuel Cell Stick™ device 10 that extend to the coldzones 30 allow for the power to be removed from the Fuel Cell Stick™device 10 with a lower loss by providing a lower resistance conductorpath. Thus, the striping technique may be used in the active area (hotzone 32) of the Fuel Cell Stick™ device 10 for making series andparallel connections to increase power, and a long stripe down the sideof the device 10 to the cold ends 30 allows that power to be efficientlyremoved from the Fuel Cell Stick™ device 10.

FIG. 37 depicts, in schematic isometric view, an embodiment similar tothat depicted in FIG. 36B, but having a single cold zone 30 at the firstend 11 a of the Fuel Cell Stick™ device 10, with the hot zone 32 beingat the second end 11 b of device 10. Multiple vertical stripes orcontact pads 44 are provided within the hot zone 32 to make the seriesand/or parallel connections, and the horizontal long stripes or contactpads 44 down the sides of the device 10 are provided from the hot zone32 to the cold zone 30 for making the low temperature solder connections46 to the positive voltage node 40 and negative voltage node 38.

One method for forming the fuel passages 14 and air passages 20 is toplace an organic material as a sacrificial layer within the green,layered structure that can then bake out during a later sintering step.To build individual Fuel Cell Stick™ devices 10 having high poweroutput, such as 1 KW or 10 KW output, the Fuel Cell Stick™ device 10must be long, wide and have a high layer count. By way of example, theFuel Cell Stick™ devices may be on the order of 12 inches to 18 incheslong. When baking the green structure to sinter the ceramic and removethe sacrificial organic material, the organic material used to form thefuel passage 14 must exit through openings 12 and 16 that form the fuelinlet and fuel outlet, respectively. Similarly, the organic materialused to form the air passage 20 must bake out through the openings 18and 22 that form the air inlet and air outlet, respectively. The longerand wider the devices, the more difficult it is for the organic materialto exit through these openings. If the device is heated too fast duringbake-out, the various layers can delaminate because the decomposition ofthe organic material occurs faster than the material can exit thestructure.

FIGS. 38A and 38B depict, in schematic cross-sectional top view, analternative embodiment that provides multiple exit gaps for bake-out ofthe organic material (sacrificial layer) 72. As shown in FIG. 38A,multiple openings 70 are provided on one side of the Fuel Cell Stick™device 10 to provide multiple bake-out paths for the organic material 72to exit the structure. As depicted in FIG. 38B, after bake-out, themultiple openings 70 are then closed by applying a barrier coating 60 tothe side of the Fuel Cell Stick™ device 10. By way of example, thebarrier coating 60 may be a glass coating. In another example, thebarrier coating 60 may be a glass containing a ceramic filler. In yetanother embodiment, the barrier coating 60 may be a contact pad 44, forexample filled with paste, which would then also serve as the lowresistance path for the generated power. The silver paste may alsocontain glass for increased adhesion. In an exemplary embodiment, thebake-out paths for the cathode 26 are vented to one side of the FuelCell Stick™ device 10 and the bake-out paths for the anode 24 are ventedto the opposing side of the device 10 to avoid shorting between oppositeelectrodes.

In an alternative embodiment for an Fuel Cell Stick™ device 10, 100,200, 300, rather than having an open air passage 20 and fuel passage 14lined with a cathode 26 or anode 24, respectively, the cathode and airchannel may be combined and the anode and fuel channel may be combinedthrough use of porous electrode materials that permit flow of the air orfuel. The cathodes and anodes must be porous anyway to permit thereaction to occur, so in combination with forced air and fuel input,sufficient flow could be achieved through the Fuel Cell Stick™ device topermit the power generating reaction to occur.

Another embodiment of the present invention is depicted in schematiccross-sectional end view in FIG. 39. This embodiment is essentially ananode-supported version of an Fuel Cell Stick™ device 10. As with otherembodiments, the Fuel Cell Stick™ device 10 may have a hot end 32 and acold end 30, or two cold ends 30 with an intermediate hot zone 32.Rather than having the device 10 supported by ceramic 29, theanode-supported version uses the anode material as the supportingstructure. Within the anode structure, a fuel passage 14 and an airpassage 20 are provided in opposing relation. The air passage 20 islined with an electrolyte layer 28, and then with a cathode layer 26.Chemical vapor deposition could be used to deposit the internal layers,or by using solutions of viscous pastes.

In FIGS. 40A and 40B, a further embodiment is shown for ananode-supported version of the Fuel Cell Stick™ device 10. In thisembodiment, the separate open fuel passage 14 is eliminated, such thatthe porous anode 24 also serves as the fuel passage 14. In addition, theFuel Cell Stick™ device 10 is coated with a barrier coating 60, such asa glass coating or a ceramic coating, to prevent the fuel from exitingout the sides of the device 10. The Fuel Cell Stick™ device 10 may haveas many air passages 14 with associated electrolyte 28 and cathode 26 inthe anode structure as desired. As depicted in FIG. 40B, the fuel fromfuel supply 34 is forced into first end 11 a through the porous anode24, which serves as the fuel passage 14, and passes through theelectrolyte layers 28 and the cathodes 26 to react with air from airsupply 36, and the spent air and fuel can then exit out the air outlet22.

In another embodiment depicted in a schematic cross-sectional end viewin FIG. 41A and a schematic cross-sectional top view in FIG. 41B, theFuel Cell Stick™ device 10 may include a plurality of air passages 20provided within the anode-supporting structure, and a single fuelpassage 14 normal to the multiple air passages 20 for feeding fuel fromthe fuel supply 34 through the single fuel inlet 12 to multiple airpassages 20. Again, the air passages 20 are lined first with anelectrolyte layer 28 and then with a cathode 26. The fuel passes fromthe single fuel passage 14 through the anode structure 24, through theelectrolyte 28, and through the cathode 26 to react with the air in theair passage 20, and the spent fuel and air exits from the air outlet 22.The spent fuel can also seep out the side of the Fuel Cell Stick™ device10 that does not include the barrier coating 60, which uncoated sidewould be located on the opposing side of the device 10 from theorientation of the single fuel passage 14.

In the embodiments pertaining to an anode-supported structure, it may beappreciated that the structure may be essentially reversed to be acathode-supported structure. Fuel passages 14 coated with an electrolytelayer 28 and an anode layer 24 would then be provided within the cathodestructure. A separate air passage 20 or multiple air passages 20 couldalso be provided, or the porosity of the cathode 26 could be used forthe air flow.

FIGS. 42A-42C depict a method for forming the electrodes within the airpassages 20 and fuel passages 14. Taking the fuel passage 14 and anode24 as an example, rather than building up a green structure layer bylayer using layers of green ceramic and metal tape layers, or printingmetallizations, in the present embodiment, the Fuel Cell Stick™ device10 is first built without the electrodes. In other words, green ceramicmaterial is used to form the electrolyte 28 and ceramic supportingportions 29 of the Fuel Cell Stick™ device 10 and the organic materialis used to form the passages, such as fuel passage 14. After the FuelCell Stick™ device 10 has been sintered, the fuel passage 14 is filledwith an anode paste or solution. The paste may be thick like that of aprinting ink, or runny like that of a high-content water solution. Theanode material can be filled into the fuel passage 14 by any desiredmeans, such as sucking it in via a vacuum, by capillary forces, orforcing it in via air pressure.

Alternatively, as shown in FIGS. 42A-42C, the anode material isdissolved in solution, flowed into the fuel passage 14, and thenprecipitated. For example, through a change of pH, the anode particlescan be precipitated and the solution drawn out. In another alternative,the anode particles can be simply allowed to settle, and then the liquiddried or baked out of the fuel passage 14. This settling can beaccomplished by creating an ink or liquid carrier that will not keep theparticles in suspension for any extended period of time, for example,due to low viscosity. A centrifuge could also be used to force thesettling. The centrifuge can easily allow preferential settling of mostparticles onto one surface of the fuel passage 14 to thereby conserveelectrode material and to ensure that only one surface of the fuelpassage 14 acts as an electrolyte.

As shown in FIG. 42A, the anode particle-containing solution 66 ispulled into the fuel passage 14 until the passage 14 is completelyfilled, as shown in FIG. 42B. The particles then settle to the bottom ofthe passage 14 to form an anode layer 24, as shown in FIG. 42C. Floodingin of the solution 66 can be accelerated by gravity, vacuum, orcentrifuge, as compared to normal capillary forces. Of course, while theanode 24 and fuel passage 14 were used as an example, any of thesealternative embodiments may also be used with a cathode paste orsolution to create a cathode layer 26 in an air passage 20.

In another alternative, a ceramic electrode material (anode or cathode)could be infused into the passage (fuel or air) in a liquid sol-gelstate, and then deposited inside the passage. It is also possible torepeat the filling operation multiple times, such as in the case wherethe concentration of the desired electrode material in the liquid islow, or to provide a gradient of properties in the electrode (such as toprovide a different amount of YSZ in the electrode close to theelectrolyte versus the amount of YSZ in the electrode farther from theelectrolyte), or if there is a desire to put multiple layers ofdissimilar materials together (such as a cathode made of LSM near theelectrolyte, and then silver over the top of the LSM for betterconductivity).

Referring back to FIGS. 7C and 7D, in which ceramic spheres or ballswere used to provide structural support to the air and fuel passages 20,14, ceramic particles may also be used to increase the effective surfacearea for a greater reaction area, thus giving a higher output. Veryfine-sized ceramic balls or particles can be used inside the fuelpassage 14 and the air passage 20 prior to applying the electrode layer.As shown in FIG. 43 in schematic cross-sectional side view, surfaceparticles 62 line the passage 14 to provide the electrolyte layer 28with an uneven topography that increases the surface area available toreceive the electrode layer. The anode 24 is then applied over theuneven topography with the anode material coating all around the surfaceparticles 62 thereby increasing the reaction area.

In an alternative embodiment, depicted in schematic cross-sectional sideview in FIG. 44, the electrolyte layer 28 may be laminated so as toprovide the uneven topography or textured surface layer 64, such as bypressing the green electrolyte layer against a fine grading having aV-shaped pattern, which pattern is then imparted to the electrolytelayer 28. After the electrolyte layer 28 is sintered to solidify theceramic and the textured surface layer 64, the anode layer 24 may thenbe applied, such as by using the backfill process described above inFIGS. 42A-42C, to provide an anode with a high reaction area.

Yet another embodiment of the invention is depicted in FIGS. 45A and45B. FIG. 45A is a schematic top view depicting the air and fuel flowthrough air and fuel passages and the arrangement of the electrodes, andFIG. 45B is a cross-sectional view through the hot zone 32. Along thelength of Fuel Cell Stick™ device 10, the device is divided into a leftside 80 and a right side 82 with an intermediate or bridging portion 84therebetween. A plurality of air passages 20L extend from the first end11 a of Fuel Cell Stick™ device 10 along the length through the leftside 80 and exit out the left side 80 adjacent second end 11 b, and aplurality of air passages 20R extend from first end 11 a along thelength through the right side 82 and exit the Fuel Cell Stick™ device 10on the right side 82 adjacent the second end 11 b. The air passages 20Lare offset from the air passages 20R, as best shown in FIG. 45B. Aplurality of fuel passages 14L extend from the second end 11 b of FuelCell Stick™ device 10 along the length through the left side 80 and exiton the left side 80 adjacent first end 11 a, and a plurality of fuelpassages 14R extend from second end 11 b along the length through theright side 82 and exit the right side 82 adjacent first end 11 a. Thefuel passages 14L are offset from the fuel passages 14R. In addition,with the exception of one fuel passage and one air passage, each fuelpassage 14L is paired with and slightly offset from an air passage 20Rand each air passage 20L is paired with and slightly offset from a fuelpassage 14R. For each offset pair of fuel passages 14L and air passages20R, a metallization extends along each fuel passage 14L from the leftside 80 to the right side 82, where it then extends along the slightlyoffset air passage 20R. Similarly, for each offset pair of fuel passages14R and air passages 20L, a metallization extends along each air passage20L from the left side 80 to the right side 82, where it then extendsalong the slightly offset fuel passage 14R. The metallization serves asan anode 24L or 24R when the metallization extends along a fuel passage14L or 14R, and the metallization serves as a cathode 26L or 26R whenthe metallization extends along an air passage 20L or 20R. In thebridging portion 84 of the Fuel Cell Stick™ device 10, where themetallizations do not extend along any air or fuel passage, themetallization simply serves as a bridge 90 between an anode and acathode. In one embodiment of the present invention, the metallizationmay comprise the same material along its length, such that the anode 24Lor 24R, the bridge 90 and the cathode 26L or 26R each comprise the samematerial. For example, the metallizations may each comprise platinummetal, which functions well as either an anode or a cathode.Alternatively, the metallization may comprise different materials. Forexample, the cathodes 26R or 26L may comprise lanthanum strontiummanganite (LSM), while the anodes 24R or 24L comprise nickel, NiO, orNiO+YSZ. The bridges 90 may comprise palladium, platinum, LSM, nickel,NiO, or NiO+YSZ. The present invention contemplates any combination ortype of materials suitable for use as a cathode or an anode, or abridging material therebetween, and the invention is not limited to thespecific materials identified above.

On one side of the Fuel Cell Stick™ device 10, shown here at the rightside 82, a fuel passage 14R is provided with an associated anode 24Rthat extends to the right edge of the Fuel Cell Stick™ device 10 toprovide the external exposed anode 25. There is no offset air passage20L associated with this fuel passage 14R, and the anode 24R need notextend into the left side 80. As depicted in FIG. 45A, an externalcontact pad 44 is applied over the exposed anode 25 and extends alongthe length of the Fuel Cell Stick™ device 10 into the cold zone 30.Negative voltage node 38 can then be connected by wire 42 and solderconnection 46 to the contact pad 44. The anode 24R could extend, asshown, to the right edge throughout the hot zone 32, or could justextend in a small tab portion to reduce the amount of electrode materialused. Also, the anode 24R could extend to the right edge of the FuelCell Stick™ device 10 along the length of the fuel passage 14R, althoughsuch embodiment would involve an unnecessary use of electrode material.

Similarly, on the other side of the Fuel Cell Stick™ device 10, shown asthe left side 80, a single air passage 20L is provided with anassociated cathode 26L that extends to the left side of the Fuel CellStick™ device 10 to form the exposed cathode 27. This air passage 20L isnot associated with an offset fuel passage 14R, and it is not necessarythat the cathode 26L extend to the right side 82. A contact pad 44 maybe applied along the exterior of the left side 80 of the Fuel CellStick™ device 10 from the exposed cathode 27 to a cold end 30, where apositive voltage node 40 may be connected via wire 42 and solderconnection 46 to the contact pad 44.

In FIG. 45B, the single fuel passage 14R and associated anode 24R areshown at the top of the right side 82, while the single air passage 20Land associated cathode 26L are shown at the bottom of the left side 80of the Fuel Cell Stick™ device 10. However, the invention is not limitedto that arrangement. For example, air passage 20L and associated cathode26L could be provided also at the top of device 10 on the left side 80,in a similar offset manner to the single fuel passage 14R and itsassociated anode 24R, but the metallization would not run from the leftside 80 through the bridging portion 84 to the right side 82. Rather,the bridge 90 would be absent such that the anode 24R is electricallyseparated from the cathode 26L. Additional arrangements are contemplatedin which a Fuel Cell Stick™ device 10 may be provided with two uniqueair pathway stacks and two unique fuel pathway stacks within a singleFuel Cell Stick™ device 10, with the cells connected in series. Theembodiment depicted in FIGS. 45A and 45B has an advantage of raising thevoltage without raising the current, and while maintaining a lowresistance. Further, this embodiment provides a high density within theFuel Cell Stick™ device 10.

In FIGS. 46A and 46B, an alternative embodiment is depicted in schematicperspective view and schematic cross-sectional view, respectively.Previous embodiments (e.g., FIG. 37) provided external stripes along theexterior sides or edges of the Fuel Cell Stick™ device 10 from the hotzone 32 to the cold zone(s) 30 to provide a path of low resistance forthe electrons to travel to the cold-end. In the embodiment of FIGS. 46Aand 46B, instead of stripes down the sides or edges of the device 10, acontact pad 44 is applied along one side and one of the top and bottomsurfaces for the external connection to the anode 24 and another contactpad 44 is applied along the opposing side and the other of the top andbottom surfaces for the external connection to the cathode 26. Thus, theelectrons have a large or wide path along which to travel, therebyproviding an even lower resistance. These large contact pads 44 that areapplied on two adjacent surfaces could be used in any of the embodimentsdisclosed herein.

In FIG. 47, yet another embodiment is depicted, in schematiccross-sectional side view, of a Fuel Cell Stick™ device 10 that takesadvantage of heat exchange principles. After the heated air and fuelpass through the active zone 33 b of the hot zone 32 (i.e., the portionof the hot zone 32 where the anode 24 is in opposing relation to thecathode 26 with an electrolyte 28 therebetween), the fuel passage 14 andair passage 20 are joined into a single exhaust passage 21. Anyun-reacted fuel will burn when combined with the heated air, thusproducing additional heat. The exhaust passage 21 travels back towardthe cold zone 30 adjacent the active zone 33 b, with the direction offlow of the exhaust (spent fuel and air) being opposite that of theincoming fuel and air in the adjacent fuel and air passages 14, 20. Theadditional heat generated in the exhaust passage 21 is transferred tothe adjacent passages 14, 20 to heat the incoming fuel and air.

FIGS. 48A-48C depict an “end-rolled Fuel Cell Stick™ device” 400 havinga thick portion 402 having a greater thickness than a thin portion 404,as depicted in FIG. 48A. The fuel and air inlets 12, 18 are positionedadjacent first end 11 a, which is at the end of thick portion 402, andwhile not shown, the air and fuel outlets (16, 22) may be provided atthe sides of the device 400 adjacent opposing second end 11 b, which isat the end of the thin portion 404. The thick portion 402 should bethick enough to provide mechanical strength. This may be achieved byproviding thick ceramic 29 around the adjacent fuel and air inlets 12,18. The thin portion 404 will include the active zone 33 b (not shown)that includes an anode (not shown) in opposing relation to a cathode(not shown) with an electrolyte (not shown) therebetween (as in priorembodiments). The thin portion 404 should be thin enough to permit it tobe rolled while in the green (unfired) state, as shown in FIG. 48B.After the thin portion 404 is rolled to a desired tightness, the device400 is fired. The rolled thin portion 404 can then be heated to causethe reaction, while the thick portion 402 is a cold end, as discussed inother embodiments. The end-rolled Fuel Cell Stick™ device 400 is a largesurface area device that can fit in a small space by virtue of rollingthe thin portion 404. Moreover, the thin cross-section of the activezone (33 b) in the thin portion 404 reduces the heat transfer out alongthe ceramic and allows good temperature cycle performance.

In embodiments in which the anode 24 and cathode 26 are exposed at theedges (sides) of the Fuel Cell Stick™ device 10 in the active (reaction)zone 32 and/or 33 b, the ceramic 29 at the top of the device 10 may berecessed in the area of the active zone 32 and/or 33 b. This allowsaccess to both the cathode 26 and anode 24 from the top for making theelectrical connections. Contact pads 44 (e.g., metallization stripes)may then be applied along the top surface of the Fuel Cell Stick™ device10 from the active zone 32 and/or 33 b to the cold zone(s) 30 to provideconnections to outside of the hot zone chamber/furnace.

In another embodiment in which the Fuel Cell Stick™ device 10 includestwo cold zones 30 at the opposing ends 11 a, 11 b and the hot zone 32 inthe middle, contact pad(s) 44 (e.g., metallization stripes) for theanode(s) 24 and/or the cathode(s) 26 can go from the hot zone 32 outtoward both ends 11 a, 11 b of the Fuel Cell Stick™ device 10, forexample, as shown in FIG. 36B. Two separate electrical connections canthen be made to each of the anode(s) 24 and cathode(s) 26. By way ofexample and not limitation, one set of connections can be used tomonitor voltage output from the cell, while the other set of connectionscan connect the load and allow the current flow. The ability to measurevoltage separately, at the cell itself, has the advantage of giving abetter idea of the total power output from the cell.

For the contact pads 44 (e.g., metallization stripes), any suitableconducting material known to those of ordinary skill in the art may beused. Examples include silver, LSM and NiO. Combinations of materialsmay also be used. In one embodiment, non-precious metal materials may beused along the surface of the Fuel Cell Stick™ device 10 in the hot zone32. LSM, for example, may be used where the atmosphere of the hot zonechamber/furnace is oxidizing. NiO, for example, may be used where theatmosphere of the hot zone chamber/furnace is reducing. In either case,however, the non-precious metal materials lose conductivity if thematerial extends outside the hot zone chamber/furnace such that themetallization material must be transitioned to a precious metal orcorrosion resistant material just before the Fuel Cell Stick™ device 10exits the hot zone chamber/furnace. Silver paste is a convenientprecious metal material. By way of further explanation, certainmaterials such as LSM will become non-conducting as the temperaturedrops from the reaction temperature to room temperature, and othermaterials such as nickel will become non-conducting when exposed to airat the cold end 30 of the device 10. Thus, the metallization materialfor the contact pads 44 in the cold end regions 30 of the Fuel CellStick™ device 10 must be conductive in air (i.e., no protectiveatmosphere) and at low temperature. Precious metals such as silver workacross the temperature/atmosphere transition area, such that themetallization material can be transitioned to the precious metal beforethe Fuel Cell Stick™ device 10 exits the hot zone chamber/furnace. Theuse of a combination of materials allows for material selection based onthe particular needs of conductance in a hot zone 32 versus a cold zone30, and allows for reducing cost by reducing the amount of expensiveprecious metals used.

As depicted in FIGS. 49A-49C, wire 92 or other physical structure isplaced into the device during the process of building up the greenlayers (FIG. 49A), the layers are then laminated with the wire 92 inplace (FIG. 49B), and then the wire 92 is removed after lamination (FIG.49C). This is useful, for example, at the entrance point of fuel or air,where the Fuel Cell Stick™ device 10 may have a length of several inchesbefore the gas flow passage 14, 20 enters the hot zone 32 (reactionregion) of the Fuel Cell Stick™ device 10. Instead of printing a polymerthat must bake out slowly in the process to form the passage, the wireprocess may be used to remove the bake-out challenge from that part ofthe Fuel Cell Stick™ device 10. By way of example and not limitation, awire 92 with a 0.010 inch diameter may be used, which will pull outeasily. The wire 92 may also be rolled flat, to form a ribbon-likephysical structure that has a similar volume as the wire, but is shorterin cross section. Because the ribbon has more surface area, a releaseagent may be applied to the surfaces thereof to keep it from sticking tothe ceramic layers during lamination. Thus, the term “wire” is intendedto broadly include various physical structures that are long and thennarrow, whether circular, oval, square, rectangular, etc. incross-section.

FIGS. 50A-50C depict an example of forming entrance channels for a 1layer Fuel Cell Stick™ device 10. In this example, rather than using agap-forming tape 94 (e.g., polymer or wax tape) to form the entire fueland oxidizer passages 14, 20, the gap-forming tape 94 is only used inthe active zone 33 b, i.e., in the regions where the anodes 24 andcathodes 26 are positioned in opposing relation with electrolyte 28therebetween. In the non-active regions where the fuel and oxidizerpassages 14, 20 do not have an associated opposed anode 24 and cathode26, wires 92 are used instead of the gap-forming tape 94. As shown, thewires 92 touch or overlap the gap-forming tape 94 so that the passages14, 20 formed by the wire 92 and the gap-forming tape 94 are continuousfrom the inlets 12, 18 to the outlets 16, 22 (not shown).

As Fuel Cell Stick™ devices 10 become more and more complicated, it canbe more and more useful to use this wire concept, for example, thecomplex bake-out challenge of a multi-layer Fuel Cell Stick™ device 10(e.g., 50 layers) can be simplified. This is in part because thechallenge for binder removal, especially in complicated structures, isthat the binder bake-out products must travel from the location thatthey are generated (from the decomposition of polymer) to the outside ofthe Fuel Cell Stick™ device 10. After a wire 92 is pulled out of thestructure, however, the path along this void is free and clear. If wires92 (or other suitable physical structure) can be put into a complicatedstructure, and then pulled out, the voids created thereby can allow manyregions within the structure for bake-out products to quickly find apath out of the structure.

Another useful purpose for the wire concept is to help with pressuredistribution within the Fuel Cell Stick™ device 10. When a single tubeis supplying air or fuel to the Fuel Cell Stick™ device 10, thendifferent flow rates may exist along the many passages/channels withinthe Fuel Cell Stick™ device 10. For example, if there are 50 airpassages 20 in the Fuel Cell Stick™ device 10, corresponding to 50active layers, then there may be one passage that has a slightly largersectional area, and one passage that has a slightly smaller sectionalarea. This can arise from random variation in the dimensions of thegap-forming materials. One solution is to limit the sectional area ofthe exit from each layer. If the cross section of the exit point fromeach layer can be precisely made, so that those sectional areas areequal, and if the sectional area of the exit point is less than the areaof the flow channel, and if the area of all those exit points is lessthat the sectional area of the input tube, then the flow will be equalon each layer. This corresponds with the practicalities of gas and fluidflow. The wire concept enables this solution. At the exit point of eachlayer, a wire 92 is inserted to make the final passage of the gas to theoutside world. For 50 layers, 50 short wire pieces are inserted. Whenthey are pulled out, each layer has a precision exit dimension (forexample, a 5 mil diameter passageway).

Thus, the present invention contemplates a multilayer Fuel Cell Stick™device 10 in which the exit points of each layer are smaller insectional area than the flow path sectional area itself. The presentinvention further contemplates a multilayer Fuel Cell Stick™ device 10in which the exit points of each layer are precision machined so thatthey have exactly the same cross sectional area at some given location.The present invention yet further contemplates a multilayer Fuel CellStick™ device 10 where all exit areas put together are smaller than thesectional area of the input. In these embodiments, the sectional area ofthe exit point is defined as being at some location in the flow paththat is beyond the end of the active portion of the layer, but beforethe end output point of the Fuel Cell Stick™ device 10. In other words,this neck-down point in the flow path does not have to be exactly at theexit point from the Fuel Cell Stick™ device 10, just somewheredownstream from the active area.

In previous embodiments, the hot zone 32 and hot zone chamber have beendiscussed. The hot zone chamber may also be referred to as a furnace.The cold zone or cold end regions 30 are positioned outside of thefurnace. The transition zone 31 is a region of the Fuel Cell Stick™device 10 adjacent the region inside the furnace. As depicted in FIG.51, the furnace wall 96 has a total thickness T. The Fuel Cell Stick™device 10 passes through this furnace wall 96. The length of the FuelCell Stick™ device 10 in the wall 96 is the X dimension and is equal tothickness T. The width of the Fuel Cell Stick™ device 10 as it passesthrough the wall 96 is the Y dimension. The thickness of the Fuel CellStick™ device 10 is the Z dimension. For purposes of this embodiment, Zis less than or equal to Y.

According to an embodiment of the invention, for optimal conditions, thefurnace wall thickness T should be greater than the width, Y, of theFuel Cell Stick™ device 10 as it passes through the wall 96. If T isless than Y, then the stress on the Fuel Cell Stick™ device 10 as itpasses through the wall 96 may be too high, and the Fuel Cell Stick™device 10 could crack.

In another embodiment, depicted in FIGS. 52A-52C, dimension L is themaximum dimension in a plane transverse to the direction of the lengthof the device 10 (i.e., in the Y-Z plane) of the Fuel Cell Stick™ device10, (100, 200, 300 or 400) at the portion where it passes through thefurnace wall 96. For a rectangular Fuel Cell Stick™ device 10 (100,400), the maximum dimension L may be the diagonal, as shown in FIG. 52B.For a tubular Fuel Cell Stick™ device 200, 300, the maximum dimension Lmay be the diameter. For optimal conditions, the dimensions should besuch that T≧½ L.

The wall thickness T may be made from one uniform material (insulation)98. Alternatively, as depicted in FIG. 53, the wall thickness T may alsobe made from multiple, graded insulation layers, such as threeinsulation layers 98 a, 98 b, 98 c, such that the heat transferproperties are optimized in each layer to give the best possibletemperature transition results. In the case of a multiple-layer furnacewall 96′, the total thickness T of all layers put together should begreater than Y and/or greater than or equal to ½ L, but the thickness ofone layer of the wall 96′ could be less than Y and/or less than ½ L.

In another embodiment, depicted in FIG. 54, a multiple-layer furnacewall 96″ is provided in which multiple layers of insulation 98 a, 98 cmay be separated by air gaps 120. In this design, there could be ahigh-temperature insulation layer 98 c close to the hot zone 32, and alower temperature insulation layer 98 a close to the cold zone 30. Anintermediate (medium) temperature zone then lies between the twoinsulation layers 98 a and 98 c, for example, corresponding totransition zone 31 or a preheat zone 33 a. This embodiment can enable alonger preheat area for the air that is flowing into the Fuel CellStick™ device 10, while not having to make the hottest area of thefurnace larger. In this embodiment, the thickness of one layer of wall96″ could be made to be less than the Y dimension of the Fuel CellStick™ device 10 and/or less than ½ L as it passes through the wall 96″.But the total dimension T of the wall 96″, including layers 98 a and 98c, and the air gap 120 would be larger than the Y dimension of the FuelCell Stick™ device 10 and/or greater than or equal to ½ L. Thisembodiment further contemplates more than two insulation layers.

Discussed above is the idea of first making the Fuel Cell Stick™ device10 without the anode and cathode, and then backfilling those elementslater. The reason for doing this can be that a certain anode or cathodematerial will densify too much at the sintering temperature of Zr, andif it is too dense then it will not allow a good reaction. Or, to say itmore generically, backfilling can be necessary if the differentcomponents of the system do not want to sinter optimally with the sametemperature profile.

It is more difficult, however, to provide the current collectors on thetop portions of the anode or cathode. A current collector 122, as shownin FIGS. 55A-55E discussed below, is known to those skilled in the artto be a high-density electrode positioned as a surface portion of ananode or cathode. It generally is a highly electrically conductive layeror matrix, like a fine wire, that can collect the electrons and movethem where they need to go. The current collector 122 may be made ofNiO, or LSM, or some other low cost material, or even preciouselectrodes. Following a backfill process for forming the anodes andcathodes, it is difficult to put on a precise current collector in auniform way. But the challenge of a current collector is different thanthat of an anode or cathode. It is desirable for the anode and cathodeto be porous, which causes the danger of over-firing; whereas thecollector is desirably dense (for good conductivity), so potentially, itcan be co-fired with the Zr. While the current collector 122 could beplaced on the electrolyte 28 before back-filling, such that the currentcollectors are under the anode and cathode, touching the electrolyte 28,this arrangement blocks active area on the electrolyte 28, which isneedlessly wasteful of active area.

In accordance with an embodiment of the invention, and as depicted inFIGS. 55A-55E, the current collectors 122 are positioned and co-fired soas to have them floating in space within the Fuel Cell Stick™ device 10.This may be accomplished by printing the current collector 122 on top ofa sacrificial first organic layer 72 a (e.g., polymer), and then coatinga sacrificial second organic layer 72 b (e.g., polymer) over the top ofthe current collector 122 as shown schematically in FIG. 55A. Thecurrent collector 122 is thereby sandwiched between two sacrificialorganic layers 72 a, 72 b, as shown in FIG. 55B. The Fuel Cell Stick™device 10 is built, including placing the sacrificial layers/currentcollector structure within a ceramic supporting structure 29, as shownin FIG. 55C, and then sintered, whereby the sacrificial organic layers72 a, 72 b disappear to form a gap 123 and the current collector 122 isleft floating in space within the gap 123, as shown in FIG. 55D. It isthen easy to backfill the porous anode or cathode into the gap 123, tocomplete the anode or cathode formation. The use of support pillars 54,as described above, may also be used, such that the floating currentcollector 122 rests on the support pillars 54, as shown in FIG. 55E, toprovide mechanical support or to standardize the location. To achievethis, periodic via holes or small gaps may be created in the firstsacrificial layer 72 a of polymer, so that the current collectormaterial would periodically print down into a hole. After binderremoval, this filled hole becomes a support pillar 54. Alternatively,zirconia balls may be added into the sacrificial polymer gap material.As the sacrificial polymer dissolves, the current collector 122 wouldstick to those balls, and the balls would stick to the ceramicsupporting structure 29, as shown in FIGS. 56A and 56B, thus providingthe support. The porous anode 24 or cathode 26 then can be backfilledinto the space, as shown in FIGS. 57A and 57B, in which the electrodeparticles 124 are held in viscous liquid 126 for the back-fill, then thedevice is dried and the particles settle and are sintered to form theanode 24 or cathode 26. The anode or cathode particles can beselectively deposited onto one side, if that is useful (by gravity or bycentrifuge).

With a current collector style that uses printed hatch lines, there maybe some variation in the gap dimension of the air or fuel passage 14, 20resulting in the passage becoming pinched or blocked at the currentcollector 122. This variation occurs due to random dimensional changesduring sintering. FIGS. 58A-58C are micrographs that show an example ofa current collector 122 that is nearly causing a blockage of a passage14, 20. The goal for the passage 14, 20 is to have clear flow. It ispossible to make the passages larger, but this will unnecessarilydecrease the density of the Fuel Cell Stick™ device 10 (thicker passagesand thicker layers lower the power density of the multi-layer device).According to one embodiment of the invention, to reduce the possibilityof the passages 14, 20 being blocked at the current collector 122, thecurrent collector lines may be buried within the porous anode 24 andcathode 26. As depicted in FIGS. 59 and 60, in which FIG. 59 shows thecurrent collectors 122 on the surfaces of the anode 24 and cathode 26and FIG. 60 shows the current collectors 122 buried into the surfaces ofthe anode 24 and cathode 26, if the current collectors 122 are buriedinto the thickness of the porous anode and cathode 24,26 (orsubstantially buried into the anode/cathode) then the current collector122 will be less likely to block the path of gas flow. FIG. 69 shows anactual current collector trace that has been recessed into the porousanode or cathode.

A method of burying the current collector 122 is shown in FIGS. 61A-61C.First, dispense or print the current collector 122 onto a temporarysubstrate 128. Then, cover this current collector 122 with the electrodematerial such as by printing a paste or backfilling with a viscousliquid 126 containing electrode particles 124 and drying. Finally,remove the temporary substrate 128. The temporary substrate 128 may be apiece of plastic with only moderate adhesion to the electrode materialafter drying such that the dried electrode-on-plastic can be turned overand the plastic peeled off. The same or similar result may be achievedby putting the current collector 122 and anode/cathode 24,26 onto thegap-forming tape 94 that is inserted into the stack, and during bake-outand sintering, the gap-forming tape 94 will disappear, leaving the sameend result.

When printing the anode 24 or cathode 26 over the top of the currentcollector 122, if the current collector 122 tends to dissolve a littleand spread out, materials with different solubilities may be used (inthe extreme case, the current collector 122 can contain resin materialthat is soluble in polar solvents, and the porous electrode ink can havea resin material soluble in non-polar solvents). It is desirable tolimit this spreading, because too much spreading of the currentcollector 122 will work to reduce the diffusion of gasses into theporous anode 24 or cathode 26. So, it is possible that some spreading ofthe current collector 122 will happen, but at least a portion of thecurrent collector 122 is desirably buried in the porous material. Thus,this invention contemplates a current collector path where some portionof the current collector 122 is recessed into the porous anode 24 orcathode 26 in order to reduce the protrusion of the current collector122 in to the fuel passage 14 or air passage 20.

In the active zone 33 b of the multilayer Fuel Cell Stick™ device 10,one would like to have the electrolyte 28 be as thin as possible, forexample, 10 μm. But a super-thin electrolyte increases the possibilityof having a leak between the air and fuel sides of the device. Thinnerelectrolyte can give higher power, but too thin will allow a crack orleak, and give zero output from the layer. According to one embodimentof this invention, a key to the minimum allowable thickness of theelectrolyte 28 in the active zone 33 b is that the anode and cathodethickness also contribute to the total thickness, and therefore to thetotal strength. By way of example only and not limitation, if 100 μm ofthickness is desired to prevent cracking, and each anode 24 and cathode26 measures 45 μm, then a 10 μm electrolyte thickness will work well.(45+45+10=100).

In the passive area (areas without an opposing anode and cathode) of amultilayer Fuel Cell Stick™ device 10, there is a different thicknessrequired. This passive area is responsible for distribution of air andfuel. This has been shown in many of the drawings as air and fueldistribution passages that overlap. The requirement here is also to havea certain thickness to prevent cracking, but without the anode 24 andcathode 26, the ceramic 29 here must be thicker than the ceramicelectrolyte layer 28 in the active zone 33 b. So in the example above,the ceramic 29 in the passive area must be 100 μm while the ceramicelectrolyte layer 28 in the active zone 33 b can be thinner, such as 10μm.

According to an embodiment of the invention, a method is provided forachieving an individual layer of ceramic electrolyte 28, 29 with twothicknesses: thicker ceramic 29 in the passive gas passages area, andthinner ceramic electrolyte 28 in the active zone 33 b. The method,depicted in FIGS. 62-62A, uses three pieces of ceramic tape 130 tocreate the ceramic 29 in the passive gas flow region, where two of thetape pieces 130 a, 130 c end and only the center layer 130 b continuesinto the active zone 33 b to serve as ceramic electrolyte 28 between theopposing anode 24 and cathode 26.

Numerous ideas are presented above in the context of an elongatestructure that exits the furnace for low temperature connections.However, many of the ideas also may be used in multi-layer Fuel Celldevices that do not exit the furnace and/or that have a plate shape orthe like. The densities of the devices achievable in the presentinvention may be achieved in other Fuel Cell devices and systems whereconnections are made to the hot Fuel Cell device in a furnace. Forexample, concepts disclosed herein that may be used in other fuel celldevices include polymer tape, polymer tape filled with round balls, awire used to form exit or entrance passages, one passage serving twoelectrodes, a paddle-shaped device, drying the electrode suspensiontowards one side by using gravity or centrifuge, side gaps fortermination and series design.

The current collector 122 has a purpose of allowing electrons that areproduced or consumed in the electrodes (anode 24 and cathode 26) totravel in a low-resistance path on their way to the load (voltage nodes38, 40). The optimal electrode design is not very conductive because itmust allow several things to happen at once: there are pores to allowthe gases to flow, there is ceramic in the electrodes to allow theoxygen ions to flow toward the electrolyte, and there are electronicconductors to let the electrons flow. The presence of the pores and theceramic means that the electrode overall will have higher resistancethan if it was only made of electronic conductor.

Once the electron is liberated, it is important to allow it to travel ona high conductivity path. Existing designs for current collectors arebased on removing the electrolyte ceramic from the conductor, but stillleaving the porosity. This creates a more conductive layer. This isprinted over the entire anode or cathode. One disadvantage of thisdesign in a multilayer structure is that if the anode/cathode materialshave to be added after sintering, it can be difficult to create twodistinct layers, as described. The advantage of co-firing a currentcollector is described above.

According to an embodiment of the invention, a current collector 122 maybe used that comprises a high-density conductor material (i.e., littleor no porosity, such that if it was printed over the entire anode 24 orcathode 26 it would inhibit the reaction), which is printed in a hatchpattern. In one embodiment, the collector is printed in a rectilinearpattern, also referred to as a hatch pattern, leaving open space betweenthe hatch marks for the gas to penetrate. Gas permeability in the porousanode 24 and cathode 26 is such that the gas that enters the porousmaterial between hatch lines will also flow under the hatch lines. Byvarying the pitch from line to line, and the line width itself, it ispossible to find an optimal geometry. By way of example, a 0.006″ linewidth and a 0.030″ line pitch may be used. FIG. 63 depicts a top view ofa current collector 122 with a hatch pattern. FIG. 64 depicts a sideview of the current collector 122 over porous anode or cathode. FIG. 65depicts an angled view, showing in order from top to bottom: currentcollector hatch, top porous electrode, electrolyte, and bottom electrode(sticking out from electrolyte because of fracture). As the active areabecomes larger, it would also be possible to vary the line width indifferent regions. Small conductor lines could feed into largerconductor lines, and larger lines could feed into still larger conductorlines.

Flexible supply tubes 50 have been described above for connecting thefuel and air supplies 34,36 to the Fuel Cell Stick™ device 10. Bystretching the supply tube 50 open, it can be slipped over one of theends 11 a,11 b of the Fuel Cell Stick™ device 10. An adhesive can holdit in place. An alternative, according to one embodiment of theinvention, is to form the end 11 a (and/or 11 b) of the Fuel Cell Stick™device 10 with indentations 132 on the sides, as depicted in FIGS.66A-66B, so that the Fuel Cell Stick™ device 10 will mechanically holdthe supply tube 50 in place. This is achieved most conveniently in thegreen state by machining the Fuel Cell Stick™ device 10 with a router orend mill.

Based on this, a connector 134 may also be used that can clamp on to theend 11 a (and/or 11 b) of the Fuel Cell Stick™ device 10, as depicted inFIGS. 67A-67B in top schematic cross-sectional and perspective view,respectively. The connector 134 may be a molded plastic with integratedelectrical contacts 136 and a gas flow pathway 138, either one or two,depending on the design of the Fuel Cell Stick™ device 10, and agas-tight seal, such as in the form of an O-ring 140, and either one ortwo electrical contacts 136 for contacting the contact pad(s) 44. If theFuel Cell Stick™ device 10 is a two ended Fuel Cell Stick™ device 10,such that one polarity is exiting the Fuel Cell Stick™ device 10 at eachend of the Fuel Cell Stick™ device 10, then the connector 134 couldstill have two or more electrical contacts 136 at each end of the FuelCell Stick™ device 10 in order to give lower resistance contacts. Theelectrical contacts 136 could be on the sides of the Fuel Cell Stick™device 10 or on the top and bottom of the Fuel Cell Stick™ device 10,the latter of which would give lower resistance because the contacts arewider.

Although not shown, the connector 134 could have two O-rings, therebyproviding two sections of sealing within the connector 134: one for air,the other for fuel. Such a connector could be used as a single connectoron a single-ended Fuel Cell Stick™ device 10, which provides positiveand negative contacts, and air and fuel delivery.

The embodiments described above included two opposing ends 11 a, 11 bfor the device. However, the concepts of the Fuel Cell Stick™ device 10described above could be applied to a device 500 that has more than 2ends or exit points leaving the furnace. For example, FIGS. 68A-68Bdepict devices having 4 points of exit. The four locations could providethe air inlet 18, air outlet 22, fuel inlet 12, and fuel outlet 16. Thiscould make it easier to recycle unburned fuel into the furnace heatingoperation. Exit points other than 2 and 4 may be used, such as 3 or 6.

The use of support balls (see FIGS. 7C-7D) may be used in Fuel Celldevices other than Fuel Cell Stick™ devices 10, for example, squareplate devices. The support balls allow large areas to be created in themultilayer structure, without having the different layers collapse oneach other. The device could have large, open areas within a genericmultilayer plate. Or, the device could have paths that were 0.5 inchwide, but many inches long, filling the area. In either case, the balltechnology disclosed herein would be advantageous.

A key idea of the balls is that they are rounded, which can preventpuncture. Because there is a need to make the electrolytes, anodes andcathodes thin (for density, and for higher performance), it is possiblefor punctures to arise from the use of irregularly shaped materials.Sand or grit could dig into the electrolyte and cause a leak. On theother hand, the electrolyte can gently deform around the balls withoutcausing leaks or tears. Similarly, the pillar concept of FIGS. 7A-7B canbe used in a multilayer Fuel Cell structure other than the Fuel CellStick™ device 10 form.

In FIGS. 38A-38B, we show the use of multiple bake-out ports that canlater be sealed over. This is an advantageous concept for any multilayerapproach to the SOFC or other fuel cell device. Again, regarding thelarge plate, the designer will have large areas of gas passages that arebeing created, and the need to remove the organic material that fillsthose spaces. Typically, however, there is only one fuel entrance point,and one fuel exit point. The same is true of the air side. With suchlarge areas of organic material, but so few exit points, it is likelythat one of the largest manufacturing challenges will be to avoiddelaminations.

The solution to this is to create numerous bake-out points, smallopenings that can allow bake-out gasses or liquids (in the case that waxis used) to come out of the structure with minimum stress on the entirestructure. After the multilayer structure is sintered, it is easy tocome back later and fill in those small bake-out points with a solidmaterial to prevent leaks (such as a glass-ceramic combination).

The wire 92 concept is a lot like the bake-out port concept above, andvery useful for a multilayer structure. Imagine making a 4 inch squareplate, with 20 or 50 active layers in the plate. You would like tocreate the bake-out ports for easier organic removal. But it would beeven better if these convenient bake-out ports could reach into thecenter of the plate. By inserting the wire 92 and then pulling it outafter lamination, this can be accomplished. The wire 92 could cut acrossseveral areas that otherwise might have very long distances to gobetween the middle of the plate and the outside world. The concept doesnot have to be a wire exactly, as discussed above. That is just the mostconvenient form, because it has a low surface area. The physical piececould be flat, for example 0.002″ thick by 0.200″ wide. In that case, itmight need to be covered with a release agent to prevent the layers fromsticking. Regardless, the idea is a physical piece that is inserted intothe structure and then removed in order to facilitate organic removal.

In another embodiment, carbon tape with wax is used as a gap-formingtape 94. A challenge is to have the gap-forming material come out evenlywithout causing splitting or delamination in the Fuel Cell Stick™devices 10. It would be better if the material could magically disappearat the right time, leaving open channels so that the other polymermaterials in the anode 24 and cathode 26 and electrolyte 28 could bakeout. One approach is to use wax. The waxes that are used for investmentcasting (the so-called lost wax method) work well melting at around 90°C., above the lamination temperature used to laminate the multilayerstructure, but below the binder burnout temperatures of 150-300° C. Butwax is not ideal because if you cast it into a 2-mil thick sheet, itdoes not have desirable strength. It is brittle to the touch. The waxshould be stronger in the thin section. The solution to this is tocombine the wax with some kind of fiber to give it strength. One choiceis carbon fiber. The carbon fiber can be purchased in a random fiberconfiguration, called mat, or in a woven fiber configuration, thatresembles actual cloth. Other fibers may also be possible. Byimpregnating the wax into carbon fiber, optimal properties can beobtained. The carbon/wax composite can be put into the multilayerstructure to form a gap. After lamination, the temperature is raised tothe melting point of the wax, and the wax then turns to liquid and runsout of the Fuel Cell Stick™ device 10. This leaves open-air pathwayswithin the carbon fibers, which allows easy bake-out of the surroundingpolymer materials inside the structure. The carbon fiber does notvolatilize (turn to CO₂) until temperatures near 750° C. Thus, it ispossible to make a structure where one of the chief gap formationmaterials disappears before binder burn-out occurs, thereby leavingclear paths for binder removal. Then, at the mid temperatures, thepolymer itself can volatilize. Finally, at the high temperatures, thecarbon fibers can disappear. FIG. 70 is an image of the gap left oncethe wax and carbon fibers are gone after sintering using this carbon-waxcombination.

While the invention has been illustrated by the description of one ormore embodiments thereof, and while the embodiments have been describedin considerable detail, they are not intended to restrict or in any waylimit the scope of the appended claims to such detail. Additionaladvantages and modifications will readily appear to those skilled in theart. The invention in its broader aspects is therefore not limited tothe specific details, representative apparatus and method andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the scope of thegeneral inventive concept.

1. A method of making a fuel cell device comprising: providing a first green ceramic layer having a first portion that will serve as an active electrolyte portion of the fuel cell device and a second portion that will serve as a passive supporting portion of the fuel cell device; applying an anode layer on the first portion of a first side of the first green ceramic layer and applying a cathode layer on the first portion on an opposing second side of the first green ceramic layer; applying a second green ceramic layer on the second portion of each of the first and second sides of the first green ceramic layer, wherein a thickness of the second green ceramic layers is approximately equal to a thickness of the anode layer and the cathode layer; applying a sacrificial layer over each of the anode and the cathode layers and second green ceramic layers; applying a third green ceramic layer over each of the sacrificial layers, wherein the first, second and third green ceramic layers are configured to be non-conductive to electrons, and the anode and cathode layers are configured to be conductive to electrons; and heating to a temperature sufficient to sinter all the layers and burn out the sacrificial layers to form a pair of gas passages with a thick sintered ceramic therebetween in the passive supporting portion and an anode, thin electrolyte and cathode therebetween in the active electrolyte portion.
 2. The method of claim 1 wherein the sacrificial layers comprise carbon fibers in a wax matrix, and wherein the heating is to a first temperature sufficient to melt out the wax without burning out the carbon fibers or a polymer binder in the green ceramic layers, then to a second temperature sufficient to burn out the polymer binder, and then to a sintering temperature sufficient to sinter the green ceramic layers and burn out the carbon fibers.
 3. A method of making a fuel cell device comprising: providing a first green ceramic layer having a first portion that will serve in an active fuel cell portion of the fuel cell device and a second portion that will serve in a passive supporting portion of the fuel cell device; applying an anode layer on the first portion of a first side of the first green ceramic layer and applying a cathode layer on the first portion on an opposing second side of the first green ceramic layer to provide a three-layer active fuel cell portion having an anode opposing a cathode with an electrolyte therebetween; applying a second green ceramic layer directly on the second portion of each of the first and second sides of the first green ceramic layer to form a three-layer passive supporting portion of ceramic lacking an anode and cathode in opposing relation, wherein a thickness of the second green ceramic layers is approximately equal to a thickness of the anode layer and the cathode layer whereby the three-layer active fuel cell portion and the three-layer passive supporting portion have approximately equal thicknesses; applying a sacrificial layer over each of the anode and the cathode layers and the second green ceramic layers; applying a third green ceramic layer over each of the sacrificial layers to provide a ceramic support structure surrounding the active fuel cell portion; and heating to a temperature sufficient to sinter all the layers and burn out the sacrificial layers to form a pair of gas passages within the ceramic support structure with a thick sintered ceramic between the pair of gas passages in the passive supporting portion and an anode, thin electrolyte and cathode between the pair of gas passages in the active fuel cell portion.
 4. The method of claim 3 wherein the sacrificial layers comprise carbon fibers in a wax matrix, and wherein the heating is to a first temperature sufficient to melt out the wax without burning out the carbon fibers or a polymer binder in the green ceramic layers, then to a second temperature sufficient to burn out the polymer binder, and then to a sintering temperature sufficient to sinter the green ceramic layers and burn out the carbon fibers.
 5. A method of making a fuel cell device comprising: providing a first support layer comprising a green ceramic support material lacking electrode particles; applying a first gas passage layer over the first support layer, wherein a first area of the first gas passage layer comprises a sacrificial material and a second area comprises the green ceramic support material; applying a first electrode layer over the first gas passage layer, wherein a first active area of the first electrode layer comprises a first electrode material and a second passive area comprises the green ceramic support material; applying a combined electrolyte and support layer comprising the green ceramic support material over the first electrode layer; applying a second electrode layer over the combined electrolyte and support layer, wherein a first active area of the second electrode layer comprises a second electrode material and is in opposing relation to the first active area of the first electrode layer, and a second passive area comprises the green ceramic support material and is in opposing relation to the second passive area of the first electrode layer; applying a second gas passage layer over the second electrode layer, wherein a first area of the second gas passage layer comprises the sacrificial material and a second area comprises the green ceramic support material; applying a second support layer comprising the green ceramic support material over the second gas passage layer; and heating to a temperature sufficient to sinter all the layers and burn out the sacrificial material to form first and second gas passages within a ceramic support structure having a thick sintered ceramic between the first and second gas passages in the second passive areas and an anode, thin electrolyte and cathode between the first and second gas passages in the first active areas.
 6. The method of claim 5 wherein the sacrificial material comprise carbon fibers in a wax matrix, and wherein the heating is to a first temperature sufficient to melt out the wax without burning out the carbon fibers or a polymer binder in the green ceramic support material, then to a second temperature sufficient to burn out the polymer binder, and then to a sintering temperature sufficient to sinter the green ceramic support material and burn out the carbon fibers. 